Pub Date : 2026-04-01Epub Date: 2025-12-17DOI: 10.1016/j.bbabio.2025.149576
Michael Lynch
A recent paper in this journal claims that prior estimates of the bioenergetic costs of producing cells are off by more than 100-fold. Here, it is shown that this conclusion is based on an erroneous interpretation of the methods previously employed by a diversity of authors and that the downstream arguments are conceptually flawed. Likewise, the author's claim that the establishment of the mitochondrion caused a quantum leap in bioenergetic capacity that spurred a revolution in eukaryotic innovation is inconsistent with empirical data and evolutionary theory.
{"title":"Energetics and evolution: Response to Martin","authors":"Michael Lynch","doi":"10.1016/j.bbabio.2025.149576","DOIUrl":"10.1016/j.bbabio.2025.149576","url":null,"abstract":"<div><div>A recent paper in this journal claims that prior estimates of the bioenergetic costs of producing cells are off by more than 100-fold. Here, it is shown that this conclusion is based on an erroneous interpretation of the methods previously employed by a diversity of authors and that the downstream arguments are conceptually flawed. Likewise, the author's claim that the establishment of the mitochondrion caused a quantum leap in bioenergetic capacity that spurred a revolution in eukaryotic innovation is inconsistent with empirical data and evolutionary theory.</div></div>","PeriodicalId":50731,"journal":{"name":"Biochimica et Biophysica Acta-Bioenergetics","volume":"1867 2","pages":"Article 149576"},"PeriodicalIF":2.7,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145794981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The mitochondrial F1FO-ATPase is a dual-function enzyme that synthesizes ATP using the proton motive force and hydrolyzes ATP to reenergize the membrane.
Mg2+ is the physiological cofactor of F1FO-ATPase, enabling both ATP synthesis and hydrolysis, while Ca2+ supports only ATP hydrolysis.
Mg2+-dependent F1FO-ATPase exhibits positive cooperativity in ATP hydrolysis Hill coefficient (nHi) of 2.01 ± 0.21, whereas Ca2+-dependent activity shows Michaelian kinetics, nHi 1.41 ± 0.06.
Ca2+ acts as an uncompetitive inhibitor on Mg2+-dependent ATP hydrolysis, suggesting distinct binding sites and conformational effects.
The differential kinetic behavior underlies the enzyme's multifunctionality of F1FO-ATPase in physio-pathological conditions, depending on the cofactor.
{"title":"Substitution of Mg2+ cofactor with Ca2+ disrupts positive cooperativity in F1FO-ATP(hydrol)ase catalysis","authors":"Cristina Algieri , Antonia Cugliari , Fabiana Trombetti , Salvatore Nesci","doi":"10.1016/j.bbabio.2025.149580","DOIUrl":"10.1016/j.bbabio.2025.149580","url":null,"abstract":"<div><div>The mitochondrial F<sub>1</sub>F<sub>O</sub>-ATPase is a dual-function enzyme that synthesizes ATP using the proton motive force and hydrolyzes ATP to reenergize the membrane.</div><div>Mg<sup>2+</sup> is the physiological cofactor of F<sub>1</sub>F<sub>O</sub>-ATPase, enabling both ATP synthesis and hydrolysis, while Ca<sup>2+</sup> supports only ATP hydrolysis.</div><div>Mg<sup>2+</sup>-dependent F<sub>1</sub>F<sub>O</sub>-ATPase exhibits positive cooperativity in ATP hydrolysis Hill coefficient (nHi) of 2.01 ± 0.21, whereas Ca<sup>2+</sup>-dependent activity shows Michaelian kinetics, nHi 1.41 ± 0.06.</div><div>Ca<sup>2+</sup> acts as an uncompetitive inhibitor on Mg<sup>2+</sup>-dependent ATP hydrolysis, suggesting distinct binding sites and conformational effects.</div><div>The differential kinetic behavior underlies the enzyme's multifunctionality of F<sub>1</sub>F<sub>O</sub>-ATPase in physio-pathological conditions, depending on the cofactor.</div></div>","PeriodicalId":50731,"journal":{"name":"Biochimica et Biophysica Acta-Bioenergetics","volume":"1867 2","pages":"Article 149580"},"PeriodicalIF":2.7,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-04-01Epub Date: 2025-12-21DOI: 10.1016/j.bbabio.2025.149578
Victor Zhong , Imre Vass , Julian J. Eaton-Rye
In Photosystem II (PS II) the D2 and D1 proteins provide binding sites for the primary (QA) and secondary (QB) plastoquinone electron acceptors, respectively. A non-heme iron is located between QA and QB that is coordinated by a bicarbonate ligand and two His residues from D1 (D1-His215 and D1-His272) and two His residues from D2 (D2-His214 and D2-His268). The symmetry of the quinone-Fe-acceptor complex extends to D1-Arg269, which has hydrogen bonds to D1-His272, and D2-Arg265 which has hydrogen bonds to D2-His268. We have examined the role of D2-Arg265 by creating the R265A and R265D mutants in the cyanobacterium Synechocystis sp. PCC 6803. Both mutants exhibited normal photoautotrophic growth, but showed a reduction in oxygen evolution in the presence of the PS II-specific electron acceptor 2,5-dimethyl-1,4-benzoquinone (DMBQ). Chlorophyll a fluorescence induction and decay kinetics were also inhibited in the presence of DMBQ and, in the presence of the native quinone, revealed slowed QA− to QB electron transfer, together with impaired exchange between the QB-binding site and the plastoquinone pool. Addition of formate further inhibited electron transfer, consistent with weakened bicarbonate binding in the mutants, and thermoluminescence measurements revealed a decreased redox gap between QA and QB. Additionally, both mutants displayed heightened sensitivity to high light. These findings demonstrate that D2-Arg265 is important for stability of the acceptor side, bicarbonate-dependent electron transfer, and an optimal QB-binding site. All of our results are also consistent with the architecture of the quinone-Fe-bicarbonate complex supporting photoprotection and regulatory roles that are unique to oxygenic photosynthesis.
{"title":"The contribution of D2-Arg265 to the molecular architecture of the quinone-Fe-bicarbonate acceptor complex of photosystem II","authors":"Victor Zhong , Imre Vass , Julian J. Eaton-Rye","doi":"10.1016/j.bbabio.2025.149578","DOIUrl":"10.1016/j.bbabio.2025.149578","url":null,"abstract":"<div><div>In Photosystem II (PS II) the D2 and D1 proteins provide binding sites for the primary (Q<sub>A</sub>) and secondary (Q<sub>B</sub>) plastoquinone electron acceptors, respectively. A non-heme iron is located between Q<sub>A</sub> and Q<sub>B</sub> that is coordinated by a bicarbonate ligand and two His residues from D1 (D1-His215 and D1-His272) and two His residues from D2 (D2-His214 and D2-His268). The symmetry of the quinone-Fe-acceptor complex extends to D1-Arg269, which has hydrogen bonds to D1-His272, and D2-Arg265 which has hydrogen bonds to D2-His268. We have examined the role of D2-Arg265 by creating the R265A and R265D mutants in the cyanobacterium <em>Synechocystis</em> sp. PCC 6803. Both mutants exhibited normal photoautotrophic growth, but showed a reduction in oxygen evolution in the presence of the PS II-specific electron acceptor 2,5-dimethyl-1,4-benzoquinone (DMBQ). Chlorophyll <em>a</em> fluorescence induction and decay kinetics were also inhibited in the presence of DMBQ and, in the presence of the native quinone, revealed slowed Q<sub>A</sub><sup><strong>−</strong></sup> to Q<sub>B</sub> electron transfer, together with impaired exchange between the Q<sub>B</sub>-binding site and the plastoquinone pool. Addition of formate further inhibited electron transfer, consistent with weakened bicarbonate binding in the mutants, and thermoluminescence measurements revealed a decreased redox gap between Q<sub>A</sub> and Q<sub>B</sub>. Additionally, both mutants displayed heightened sensitivity to high light. These findings demonstrate that D2-Arg265 is important for stability of the acceptor side, bicarbonate-dependent electron transfer, and an optimal Q<sub>B</sub>-binding site. All of our results are also consistent with the architecture of the quinone-Fe-bicarbonate complex supporting photoprotection and regulatory roles that are unique to oxygenic photosynthesis.</div></div>","PeriodicalId":50731,"journal":{"name":"Biochimica et Biophysica Acta-Bioenergetics","volume":"1867 2","pages":"Article 149578"},"PeriodicalIF":2.7,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145821800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-21DOI: 10.1016/j.bbabio.2026.149589
Natalia A Krupenina, Alexander A Bulychev, Anna V Alova, Florian von Ruling, Alexey Eremin
Internodal cells of Characeae exposed to flickering spotted illumination mobilize long-range interchloroplast communications between the point of local light stress and non-treated cell areas. The signaling and functional coordination between immobile chloroplasts involves the export of excess products from light-stressed plastids, the lateral transport by the streaming cytoplasm, the entry of delivered substances to dimly lit recipient chloroplasts, and metabolic responses to the entered agents. There is indirect evidence that interchloroplast communications are mediated by two types of metabolites produced during photosynthetic electron transport: reducing agents such as NAD(P)H and the product of oxygen reduction H2O2 as the most stable ROS form. The involvement of these substances in intracellular signaling was tested in this study using local extracellular application of subnanomolar quantities of H2O2 and the cytoplasmic microinjection of NADH in combination with Microscopy-PAM chlorophyll fluorometry and confocal laser scanning microscopy. The pointed introduction of the above agents affected the actual and maximal chlorophyll (Chl) fluorescence yields (F' and Fm') in chloroplasts exposed to dim background light but had no effect in darkened cells. The Chl fluorescence changes induced by NADH and H2O2 featured opposite polarities, indicating the plastoquinone reduction (via segments of cyclic electron-transport pathways) and the development of non-photochemical quenching, respectively. The ability of externally applied H2O2 to move with the cytoplasmic flow has been revealed; it confirms that H2O2 can act in plant cells as a transportable signaling substance. The results provide evidence for participation of reducing substances and the oxidizing agent H2O2 in interchloroplast communications.
{"title":"Cyclosis-mediated transport and redox regulation of chloroplast activity probed by local microinjection in characean alga.","authors":"Natalia A Krupenina, Alexander A Bulychev, Anna V Alova, Florian von Ruling, Alexey Eremin","doi":"10.1016/j.bbabio.2026.149589","DOIUrl":"https://doi.org/10.1016/j.bbabio.2026.149589","url":null,"abstract":"<p><p>Internodal cells of Characeae exposed to flickering spotted illumination mobilize long-range interchloroplast communications between the point of local light stress and non-treated cell areas. The signaling and functional coordination between immobile chloroplasts involves the export of excess products from light-stressed plastids, the lateral transport by the streaming cytoplasm, the entry of delivered substances to dimly lit recipient chloroplasts, and metabolic responses to the entered agents. There is indirect evidence that interchloroplast communications are mediated by two types of metabolites produced during photosynthetic electron transport: reducing agents such as NAD(P)H and the product of oxygen reduction H<sub>2</sub>O<sub>2</sub> as the most stable ROS form. The involvement of these substances in intracellular signaling was tested in this study using local extracellular application of subnanomolar quantities of H<sub>2</sub>O<sub>2</sub> and the cytoplasmic microinjection of NADH in combination with Microscopy-PAM chlorophyll fluorometry and confocal laser scanning microscopy. The pointed introduction of the above agents affected the actual and maximal chlorophyll (Chl) fluorescence yields (F' and F<sub>m</sub>') in chloroplasts exposed to dim background light but had no effect in darkened cells. The Chl fluorescence changes induced by NADH and H<sub>2</sub>O<sub>2</sub> featured opposite polarities, indicating the plastoquinone reduction (via segments of cyclic electron-transport pathways) and the development of non-photochemical quenching, respectively. The ability of externally applied H<sub>2</sub>O<sub>2</sub> to move with the cytoplasmic flow has been revealed; it confirms that H<sub>2</sub>O<sub>2</sub> can act in plant cells as a transportable signaling substance. The results provide evidence for participation of reducing substances and the oxidizing agent H<sub>2</sub>O<sub>2</sub> in interchloroplast communications.</p>","PeriodicalId":50731,"journal":{"name":"Biochimica et Biophysica Acta-Bioenergetics","volume":" ","pages":"149589"},"PeriodicalIF":2.7,"publicationDate":"2026-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147505263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-19DOI: 10.1016/j.bbabio.2026.149588
Romain La Rocca, Pi-Cheng Tsai, Koji Kato, Yoshiki Nakajima, Fusamichi Akita, Jian-Ren Shen
Photosystem I (PSI) converts light energy into chemical energy in photosynthesis, and forms supercomplexes with light-harvesting complexes in eukaryotes to enhance energy capture and transfer. Various numbers and organizations of both PSI core and LHCI subunits are observed in various organisms. A subgroup of haptophytes named coccolithophores play a major role in marine carbon cycle and CaCO3 production, and the light-harvesting antennas of them are named FCPs (fucoxanthin-chlorophyll a/c binding protein) because they bind chlorophyll c and fucoxanthin in addition to chlorophyll a. A structure of a large PSI-FCPI supercomplex containing 38 FCPI subunits has been reported from a coccolithophore Emiliania huxleyi recently (L. Shen et al., Science 389, eadv2132, 2025). Here we solved five cryo-electron microscopy (cryo-EM) structures of PSI-FCPI supercomplexes isolated from another coccolithophore Chrysotila roscoffensis with different detergents at resolutions ranging from 2.3 to 1.7 Å. These structures represent discrete PSI-FCPIs containing 1, 4, 6, 8 and 9 FCPI subunits, with FCPIs arranged in a modular fashion. Association of each FCPI module to the PSI core, as well as the arrangement of protein subunits and pigments, are revealed. Contributions of individual antenna modules to excitation energy transfer were calculated and compared with PSI-FCPI supercomplexes from other species of coccolithophores and haptophytes. These results pinpoint the assembly of stable PSI-FCPI supercomplexes in C. roscoffensis and provide insights into how antenna modules contribute to energy transfer in coccolithophores.
{"title":"Multiple structures of photosystem I-FCPI supercomplexes from a coccolithophore alga reveal a modular antenna organization.","authors":"Romain La Rocca, Pi-Cheng Tsai, Koji Kato, Yoshiki Nakajima, Fusamichi Akita, Jian-Ren Shen","doi":"10.1016/j.bbabio.2026.149588","DOIUrl":"https://doi.org/10.1016/j.bbabio.2026.149588","url":null,"abstract":"<p><p>Photosystem I (PSI) converts light energy into chemical energy in photosynthesis, and forms supercomplexes with light-harvesting complexes in eukaryotes to enhance energy capture and transfer. Various numbers and organizations of both PSI core and LHCI subunits are observed in various organisms. A subgroup of haptophytes named coccolithophores play a major role in marine carbon cycle and CaCO<sub>3</sub> production, and the light-harvesting antennas of them are named FCPs (fucoxanthin-chlorophyll a/c binding protein) because they bind chlorophyll c and fucoxanthin in addition to chlorophyll a. A structure of a large PSI-FCPI supercomplex containing 38 FCPI subunits has been reported from a coccolithophore Emiliania huxleyi recently (L. Shen et al., Science 389, eadv2132, 2025). Here we solved five cryo-electron microscopy (cryo-EM) structures of PSI-FCPI supercomplexes isolated from another coccolithophore Chrysotila roscoffensis with different detergents at resolutions ranging from 2.3 to 1.7 Å. These structures represent discrete PSI-FCPIs containing 1, 4, 6, 8 and 9 FCPI subunits, with FCPIs arranged in a modular fashion. Association of each FCPI module to the PSI core, as well as the arrangement of protein subunits and pigments, are revealed. Contributions of individual antenna modules to excitation energy transfer were calculated and compared with PSI-FCPI supercomplexes from other species of coccolithophores and haptophytes. These results pinpoint the assembly of stable PSI-FCPI supercomplexes in C. roscoffensis and provide insights into how antenna modules contribute to energy transfer in coccolithophores.</p>","PeriodicalId":50731,"journal":{"name":"Biochimica et Biophysica Acta-Bioenergetics","volume":" ","pages":"149588"},"PeriodicalIF":2.7,"publicationDate":"2026-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147494544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-11-22DOI: 10.1016/j.bbabio.2025.149574
Italo Lorandi , José Alfredo Hernández-Zúñiga , Mercedes Esparza-Perusquía , Genaro Matus-Ortega , Héctor Vázquez-Meza , Héctor Flores-Herrera , Juan Pablo Pardo , Federico Martínez , Oscar Flores-Herrera
Complex I is absent in mitochondria from Saccharomyces cerevisiae; instead, three rotenone-insensitive NADH dehydrogenases are present: two on the external (Nde1 and Nde2) and one on the internal (Ndi1) leaf of the inner mitochondrial membrane. In a previous work (1), we reported the presence of a supercomplex in S. cerevisiae constituted by the Ndi1 and complexes III2 and IV with an apparent MW of 1600 kDa. In this work, respirasomes from WT and NDE1Δ/NDE2Δ strains were isolated, and their activities characterized. Kinetic characterization of NADH:DBQ oxidoreductase activity from respirasomes, as well as free Ndi1, showed Vmax values of 0.85 ± 0.01, 0.82 ± 0.02, and 0.51 ± 0.02 μmol NADH oxidized·min−1·mg−1 for WT respirasome, NDE1Δ/NDE2Δ respirasome, and free Ndi1, respectively. The kinetic model for WT- and NDE1Δ/NDE2Δ respirasome was a Ping Pong Bi-Bi mechanism with two different stable enzyme forms, free (E) and modified enzyme (F); while the free Ndi1 exhibited a Random Bi-Bi mechanism with the ternary complex NADH-Ndi1-ubiquinone. This suggests that the interaction of Ndi1 with complexes III2 and IV in the respirasome modifies its kinetic mechanism. Oxygen consumption values were 0.35 ± 0.07 and 0.34 ± 0.07 μmol O2·min−1·mg−1 for WT and NDE1Δ/NDE2Δ respirasomes, respectively. The values for NADH/O2 ratio were 2.4 ± 1.4 and 2.4 ± 1.6 for WT and NDE1Δ/NDE2Δ respirasomes, respectively, suggesting that electron flux from NADH to oxygen occurs in the S. cerevisiae respirasome. The electron transfer from NADH to oxygen was inhibited by flavone, antimycin A, or cyanide, but the NADH dehydrogenase activity of the respirasome was insensitive to antimycin A or cyanide, indicating that no codependence of respirasomal-Ndi1 activity occurs as reported in the Ustilago maydis respirasome. This result indicates that the activity of respirasomal Ndi1 may contribute to the quinol pool with no evidence of direct substrate channeling. This is the first evidence of the Ndi1 role as the electron input in the respirasome from S. cerevisiae.
{"title":"The internal alternative NADH dehydrogenase (Ndi1) is the electron input in the Saccharomyces cerevisiae respirasome","authors":"Italo Lorandi , José Alfredo Hernández-Zúñiga , Mercedes Esparza-Perusquía , Genaro Matus-Ortega , Héctor Vázquez-Meza , Héctor Flores-Herrera , Juan Pablo Pardo , Federico Martínez , Oscar Flores-Herrera","doi":"10.1016/j.bbabio.2025.149574","DOIUrl":"10.1016/j.bbabio.2025.149574","url":null,"abstract":"<div><div>Complex I is absent in mitochondria from <em>Saccharomyces cerevisiae</em>; instead, three rotenone-insensitive NADH dehydrogenases are present: two on the external (Nde1 and Nde2) and one on the internal (Ndi1) leaf of the inner mitochondrial membrane. In a previous work (1), we reported the presence of a supercomplex in <em>S. cerevisiae</em> constituted by the Ndi1 and complexes III<sub>2</sub> and IV with an apparent MW of 1600 kDa. In this work, respirasomes from WT and <em>NDE1Δ/NDE2Δ</em> strains were isolated, and their activities characterized. Kinetic characterization of NADH:DBQ oxidoreductase activity from respirasomes, as well as free Ndi1, showed V<sub>max</sub> values of 0.85 ± 0.01, 0.82 ± 0.02, and 0.51 ± 0.02 μmol NADH oxidized·min<sup>−1</sup>·mg<sup>−1</sup> for WT respirasome, <em>NDE1Δ/NDE2Δ</em> respirasome, and free Ndi1, respectively. The kinetic model for WT- and <em>NDE1Δ/NDE2Δ</em> respirasome was a Ping Pong Bi-Bi mechanism with two different stable enzyme forms, free (E) and modified enzyme (F); while the free Ndi1 exhibited a Random Bi-Bi mechanism with the ternary complex NADH-Ndi1-ubiquinone. This suggests that the interaction of Ndi1 with complexes III<sub>2</sub> and IV in the respirasome modifies its kinetic mechanism. Oxygen consumption values were 0.35 ± 0.07 and 0.34 ± 0.07 μmol O<sub>2</sub>·min<sup>−1</sup>·mg<sup>−1</sup> for WT and <em>NDE1Δ/NDE2Δ</em> respirasomes, respectively. The values for NADH/O<sub>2</sub> ratio were 2.4 ± 1.4 and 2.4 ± 1.6 for WT and <em>NDE1Δ/NDE2Δ</em> respirasomes, respectively, suggesting that electron flux from NADH to oxygen occurs in the <em>S. cerevisiae</em> respirasome. The electron transfer from NADH to oxygen was inhibited by flavone, antimycin A, or cyanide, but the NADH dehydrogenase activity of the respirasome was insensitive to antimycin A or cyanide, indicating that no codependence of respirasomal-Ndi1 activity occurs as reported in the <em>Ustilago maydis</em> respirasome. This result indicates that the activity of respirasomal Ndi1 may contribute to the quinol pool with no evidence of direct substrate channeling. This is the first evidence of the Ndi1 role as the electron input in the respirasome from <em>S. cerevisiae</em>.</div></div>","PeriodicalId":50731,"journal":{"name":"Biochimica et Biophysica Acta-Bioenergetics","volume":"1867 1","pages":"Article 149574"},"PeriodicalIF":2.7,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145589806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Under drought, lack of an electron source (water) reduces the capacity of oxygen-evolving photosynthesis.
•
Consequently, even under low light, excess excitation energy may be generated, which is harmful as it leads to generation of reactive oxygen species.
•
When the desert green alga Chlorella ohadii undergoes desiccation, first photosystem II binds to photosystem I via LHCII to establish energy transfer pathways, and then excitation energy dissipation induced by a quencher is initiated.
•
This strategy may provide efficient protection of the entire photosynthetic apparatus during early stages of desiccation, when the available quencher may be insufficient.
{"title":"Increase in spillover and excitation energy dissipation during wet–dry transitions in the desert green alga Chlorella ohadii","authors":"Soma Kawamura , Makio Yokono , Chiyo Noda , Jun Minagawa","doi":"10.1016/j.bbabio.2025.149573","DOIUrl":"10.1016/j.bbabio.2025.149573","url":null,"abstract":"<div><div><ul><li><span>•</span><span><div>Under drought, lack of an electron source (water) reduces the capacity of oxygen-evolving photosynthesis.</div></span></li><li><span>•</span><span><div>Consequently, even under low light, excess excitation energy may be generated, which is harmful as it leads to generation of reactive oxygen species.</div></span></li><li><span>•</span><span><div>When the desert green alga <em>Chlorella ohadii</em> undergoes desiccation, first photosystem II binds to photosystem I via LHCII to establish energy transfer pathways, and then excitation energy dissipation induced by a quencher is initiated.</div></span></li><li><span>•</span><span><div>This strategy may provide efficient protection of the entire photosynthetic apparatus during early stages of desiccation, when the available quencher may be insufficient.</div></span></li></ul></div></div>","PeriodicalId":50731,"journal":{"name":"Biochimica et Biophysica Acta-Bioenergetics","volume":"1867 1","pages":"Article 149573"},"PeriodicalIF":2.7,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145092999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01Epub Date: 2025-09-04DOI: 10.1016/j.bbabio.2025.149571
Victor V. Lemeshko
A recent revision of the chemiosmotic theory was reported by Hernansanz-Agustín and coauthors as a discovery that a Na+ gradient across the mitochondrial inner membrane equates with the H+ gradient and contributes up to half of the inner membrane potential, without an explanation of the possible underlying mechanism. Based on the experimental data of these and other authors, and performed biophysical estimations, I propose a mechanism by which both the reported fast-acting Na+/H+ exchanger, associated with the complex I of the respiratory chain, and Na+ electrodiffusion in the intracristae space and the matrix allow maintenance of a high membrane potential.
{"title":"Mechanism of Na+ ions contribution to the generation and maintenance of a high inner membrane potential in mitochondria","authors":"Victor V. Lemeshko","doi":"10.1016/j.bbabio.2025.149571","DOIUrl":"10.1016/j.bbabio.2025.149571","url":null,"abstract":"<div><div>A recent revision of the chemiosmotic theory was reported by Hernansanz-Agustín and coauthors as a discovery that a Na<sup>+</sup> gradient across the mitochondrial inner membrane equates with the H<sup>+</sup> gradient and contributes up to half of the inner membrane potential, without an explanation of the possible underlying mechanism. Based on the experimental data of these and other authors, and performed biophysical estimations, I propose a mechanism by which both the reported fast-acting Na<sup>+</sup>/H<sup>+</sup> exchanger, associated with the complex I of the respiratory chain, and Na<sup>+</sup> electrodiffusion in the intracristae space and the matrix allow maintenance of a high membrane potential.</div></div>","PeriodicalId":50731,"journal":{"name":"Biochimica et Biophysica Acta-Bioenergetics","volume":"1867 1","pages":"Article 149571"},"PeriodicalIF":2.7,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145007521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-01Epub Date: 2025-08-25DOI: 10.1016/j.bbabio.2025.149570
Andrei G. Yakovlev , Alexandra S. Taisova
Photosynthesis in bacteria, algae, and plants begins with the absorption of light energy by (bacterio)chlorophyll molecules, part of which is then converted into heat, leading to a transient change in molecular temperature. We investigated this phenomenon in reaction centers (RCs) of the purple bacterium Rhodobacter (Rba.) sphaeroides using picosecond fluorescence spectroscopy. Exclusion of charge separation processes using the VR(L157) mutation allowed us to record the spectral dynamics of fluorescence of monomeric BChl a molecules. We found that excitation of RCs into the Soret band results in significant heating of BChl a by ~160 K with subsequent vibrational cooling, which manifests itself in a dynamic narrowing of the BChl a fluorescence spectrum with two characteristic times of 5 and 16 ps. The weaker heating by ~65 K and cooling with a characteristic time of 7.5 ps are observed upon excitation of RCs into the Qx band. Excitation into the Qу band does not result in any noticeable heating of BChl a. Difference absorption spectroscopy of tryptophan in the 280 nm region showed that the observed dynamics of the BChl a fluorescence spectrum are not associated with the dielectric rearrangement of the RCs protein matrix. Analysis of the obtained data using the phenomenological model of vibrational cooling led to the conclusion that during heat diffusion from excited BChl a, several amino acid residues from the immediate environment of BChl a act as the first solvation shell (FSS). At the first, faster stage, heat is transferred from BChl a to FSS, and at the second stage, FSS transfers heat to the protein matrix of RCs. Our work has shown the importance of taking into account vibrational cooling when studying the primary processes of photosynthesis.
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Acetogenins isolated from the Annonaceae plant family are potent inhibitors of mitochondrial NADH-ubiquinone (UQ) oxidoreductase (complex I). Since acetogenins have a markedly different chemical framework from other complex I inhibitors, studying their inhibitory action offers valuable insights into the mechanism of complex I inhibition. A cryo-EM structure of mouse complex I with a bound ~35 Å-long acetogenin derivative suggested that acetogenins bind along the full length of the predicted UQ-accessing tunnel, with their γ-lactone ring orientating toward the iron‑sulfur cluster N2. However, this binding mode does not fully explain the structure–activity relationships of various acetogenin derivatives. To further elucidate their inhibition mechanism, we conducted photoaffinity labeling experiments in bovine heart SMPs using a photoreactive acetogenin derivative DLA-1, containing a small photolabile diazirine near the γ-lactone ring. DLA-1 labeled both the complex I subunits 49-kDa and ND1, which define the architecture of “top” and “bottom” regions of the canonical UQ-accessing tunnel, respectively. Proteomic analysis revealed that the labeled sites in ND1 are not within the tunnel's interior, whereas in the case of 49-kDa subunit, part of the tunnel's inner region is labeled. To investigate the molecular basis of acetogenin binding, we performed atomistic molecular dynamics simulations of DLA-1 and a natural-type acetogenin analog in the UQ-accessing tunnel. The simulation data indicate that DLA-1 is relatively rigid yet adopts multiple conformations and interacts with several regions in the tunnel including the residues identified by photoaffinity labeling. Based on these results, we discuss the binding modes of acetogenin analogs to complex I.
{"title":"Dynamic binding of acetogenin-type inhibitors to mitochondrial complex I revealed by photoaffinity labeling","authors":"Misaki Nishida , Cristina Pecorilla , Takahiro Masuya , Keitaro Hirano , Masato Abe , Oleksii Zdorevskyi , Vivek Sharma , Hideto Miyoshi , Masatoshi Murai","doi":"10.1016/j.bbabio.2025.149566","DOIUrl":"10.1016/j.bbabio.2025.149566","url":null,"abstract":"<div><div>Acetogenins isolated from the <em>Annonaceae</em> plant family are potent inhibitors of mitochondrial NADH-ubiquinone (UQ) oxidoreductase (complex I). Since acetogenins have a markedly different chemical framework from other complex I inhibitors, studying their inhibitory action offers valuable insights into the mechanism of complex I inhibition. A cryo-EM structure of mouse complex I with a bound ~35 Å-long acetogenin derivative suggested that acetogenins bind along the full length of the predicted UQ-accessing tunnel, with their γ-lactone ring orientating toward the iron‑sulfur cluster N2. However, this binding mode does not fully explain the structure–activity relationships of various acetogenin derivatives. To further elucidate their inhibition mechanism, we conducted photoaffinity labeling experiments in bovine heart SMPs using a photoreactive acetogenin derivative DLA-1, containing a small photolabile diazirine near the γ-lactone ring. DLA-1 labeled both the complex I subunits 49-kDa and ND1, which define the architecture of “top” and “bottom” regions of the canonical UQ-accessing tunnel, respectively. Proteomic analysis revealed that the labeled sites in ND1 are not within the tunnel's interior, whereas in the case of 49-kDa subunit, part of the tunnel's inner region is labeled. To investigate the molecular basis of acetogenin binding, we performed atomistic molecular dynamics simulations of DLA-1 and a natural-type acetogenin analog in the UQ-accessing tunnel. The simulation data indicate that DLA-1 is relatively rigid yet adopts multiple conformations and interacts with several regions in the tunnel including the residues identified by photoaffinity labeling. Based on these results, we discuss the binding modes of acetogenin analogs to complex I.</div></div>","PeriodicalId":50731,"journal":{"name":"Biochimica et Biophysica Acta-Bioenergetics","volume":"1866 4","pages":"Article 149566"},"PeriodicalIF":3.4,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144545921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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