Journal of Inorganic Biochemistry最新文献

{"title":"Ascorbate-enabled C-H bond amination catalyzed by myoglobin reconstituted with a trifluoromethyl-substituted Iron porphyrin","authors":"Chihiro Sonoda,&nbsp;Takashi Hayashi","doi":"10.1016/j.jinorgbio.2025.113207","DOIUrl":"10.1016/j.jinorgbio.2025.113207","url":null,"abstract":"<div><div>Nitrogen-containing organic molecules are essential structural motifs in bioactive compounds, pharmaceuticals and functional materials. Direct C-H amination via nitrene transfer provides an efficient and atom-economical route for C-N bond formation. However, most hemoprotein-based catalysts require strong reductants such as dithionite to generate the metal–nitrene intermediate. Here, we report myoglobin reconstituted with an iron complex (FePor(CF₃)₂) bearing two trifluoromethyl groups at the pyrrole β-positions of the porphyrin framework. This arrangement promotes intramolecular benzylic C-H bond amination under mild conditions using sodium <span>l</span>-ascorbate as the sole reductant. The FePor(CF₃)₂ cofactor exhibits a positively shifted Fe(III)/Fe(II) redox potential that allows efficient reduction to occur in the protein scaffold and suppresses noncatalytic substrate reduction, leading to improved chemoselectivity for secondary C-H bond amination. The H64A mutant of myoglobin reconstituted with FePor(CF₃)₂ achieved a turnover number (TON) of 133 for tertiary benzylic C-H amination. Kinetic studies revealed that the reaction rate is inversely correlated with the C-H bond dissociation energy, with a smaller negative slope in the bond dissociation energies (BDEs) plot compared to a synthetic cofactor with a negative redox potential. This suggests that there is a mechanistic shift in the rate-determining step from hydrogen atom transfer to nitrene formation. These findings highlight the potential of cofactor redox tuning to control reactivity and selectivity in artificial heme enzymes for abiological C-H bond functionalization.</div></div>","PeriodicalId":364,"journal":{"name":"Journal of Inorganic Biochemistry","volume":"277 ","pages":"Article 113207"},"PeriodicalIF":3.2,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145909877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cyclometalated iridium complex as a PD-L1 inhibitor: Suppressing expression via COX-2 blockade","authors":"Yating Zhang ,&nbsp;Jingyue Zhao ,&nbsp;Zhengqi Shen ,&nbsp;Xiangyu Dai ,&nbsp;Peisen Wang ,&nbsp;Zhi Su ,&nbsp;Suxing Jin ,&nbsp;Xuling Xue ,&nbsp;Hong-Ke Liu","doi":"10.1016/j.jinorgbio.2025.113198","DOIUrl":"10.1016/j.jinorgbio.2025.113198","url":null,"abstract":"<div><div>Metal-based Programmed Cell Death Ligand 1 (PD-L1) inhibitors partially overcome the limitations of small-molecule inhibitors, such as ambiguous targeting and complex synthetic processes. This study explores a cyclometalated iridium(III) complex Ir-FA by incorporating bioactive natural product trans-ferulic acid (FA), which could be a promising metal-based PD-L1 inhibitor. Ir-FA demonstrated selective cytotoxicity against A549 cells while exhibiting no toxicity toward normal HLF cell line. Mechanistic studies revealed that Ir-FA induces mitochondrial dysfunction via reactive oxygen species (ROS) overproduction and membrane potential collapse. Concurrently, Ir-FA effectively suppressed the expression and activity of key inflammatory mediators, cyclooxygenase-2 (COX-2) and its downstream product prostaglandin E2 (PGE2). Crucially, this combined action, mitochondrial impairment and COX-2/PGE2 inhibition, resulted in the marked downregulation of intracellular PD-L1 expression, which might help suppress the tumor immune evasion. These findings highlight the potential of exploiting the synergistic effects of iridium coordination chemistry and anti-inflammatory activity to develop innovative metal-based agents targeting the Programmed Cell Death Protein 1/PD-L1 immune checkpoint pathway. This work created a transformative platform for developing multifunctional metallodrugs with synergizing chemotherapy and immune activation, holding significant value for cancer treatment.</div></div>","PeriodicalId":364,"journal":{"name":"Journal of Inorganic Biochemistry","volume":"277 ","pages":"Article 113198"},"PeriodicalIF":3.2,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145839080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structural and mechanistic insights into the sulfur transfer protein SufU from Staphylococcus aureus","authors":"Emily Sabo ,&nbsp;Connor Nelson ,&nbsp;Delanie Huntoon ,&nbsp;Jing Yang ,&nbsp;Martin Kirk ,&nbsp;Simon J. George ,&nbsp;Brian Bennett ,&nbsp;Jeffrey M. Boyd ,&nbsp;Richard C. Holz","doi":"10.1016/j.jinorgbio.2025.113205","DOIUrl":"10.1016/j.jinorgbio.2025.113205","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Substitution of the active site Zn&lt;sup&gt;2+&lt;/sup&gt; ion in the sulfur transfer protein (SufU) from &lt;em&gt;Staphylococcus aureus&lt;/em&gt; (&lt;em&gt;Sa&lt;/em&gt;SufU) with a catalytically active Co&lt;sup&gt;2+&lt;/sup&gt; ion revealed a S&lt;sup&gt;−&lt;/sup&gt;➔Co&lt;sup&gt;2+&lt;/sup&gt; ligand-to-metal-charge-transfer (LMCT) band at 340 nm with an &lt;em&gt;ε&lt;/em&gt; of &lt;em&gt;∼&lt;/em&gt;&lt;span&gt;&lt;math&gt;&lt;mn&gt;2,760&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msup&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;msup&gt;&lt;mi&gt;cm&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt;, as well as &lt;em&gt;d-d&lt;/em&gt; (i.e. ligand field) absorption bands at 584 nm (&lt;em&gt;ε&lt;/em&gt; = 540 &lt;span&gt;&lt;math&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msup&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;msup&gt;&lt;mi&gt;cm&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt;), 636 nm (&lt;em&gt;ε&lt;/em&gt; = 580 &lt;span&gt;&lt;math&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msup&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;msup&gt;&lt;mi&gt;cm&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt;) and 735 nm (&lt;em&gt;ε&lt;/em&gt; = 220 &lt;span&gt;&lt;math&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msup&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;msup&gt;&lt;mi&gt;cm&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt;). These data suggest a distorted four- or five-coordinate Co&lt;sup&gt;2+&lt;/sup&gt; center ligated by 3 Cys residues with a dissociation constant (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;/math&gt;&lt;/span&gt;of ∼&lt;span&gt;&lt;math&gt;&lt;mn&gt;600&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;M. Co K-edge absorption spectra (XAS) of Co&lt;sup&gt;2+&lt;/sup&gt;-&lt;em&gt;Sa&lt;/em&gt;SufU indicated five-coordinate Co&lt;sup&gt;2+&lt;/sup&gt;, while extended X-ray absorption fine structure (EXAFS) spectra of Co&lt;sup&gt;2+&lt;/sup&gt;-&lt;em&gt;Sa&lt;/em&gt;SufU revealed 2 N/O and 3 S ligands. EXAFS data for Zn&lt;sup&gt;2+&lt;/sup&gt;-&lt;em&gt;Sa&lt;/em&gt;SufU revealed 1 N/O and 3 S ligands consistent with the proposed Cys&lt;sub&gt;3&lt;/sub&gt;Asp coordinating residues. The fifth ligand in the Co&lt;sup&gt;2+&lt;/sup&gt;-SaSufU enzyme is either a bidentate the active site Asp ligand or an exogenous water. Upon the addition of &lt;em&gt;Sa&lt;/em&gt;SufS to either Zn&lt;sup&gt;2+&lt;/sup&gt;-&lt;em&gt;Sa&lt;/em&gt;SufU or Co&lt;sup&gt;2+&lt;/sup&gt;-&lt;em&gt;Sa&lt;/em&gt;SufU, XAS and EXAFS data suggest that one of the S ligands is displaced by an N/O atom donor. Interestingly, electronic absorption data suggest that this only occurs in the presence of Cys. EPR analysis of Co&lt;sup&gt;2+&lt;/sup&gt;&lt;em&gt;-Sa&lt;/em&gt;SufU revealed temperature- and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;-dependent transitions within both the &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mfrac&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mfrac&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mfrac&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mfrac&gt;&lt;/math&gt;&lt;/span&gt; doublets of the &lt;span&gt;&lt;math&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mfrac&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mfrac&gt;&lt;/math&gt;&lt;/span&gt; spin system that suggested either heterogeneity of the electronic structure or an unusually small zero-field splitting for Co(II). Taken together, these data provide in-solution evidence for the mechanism of S&lt;sup&gt;2−&lt;/sup&gt; transfer from &lt;em&gt;Sa&lt;/em&gt;SufS to &lt;em&gt;Sa&lt;/em","PeriodicalId":364,"journal":{"name":"Journal of Inorganic Biochemistry","volume":"277 ","pages":"Article 113205"},"PeriodicalIF":3.2,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145861648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Carbon monoxide chemistry of α-V70I Mo-nitrogenase: Evidence from EPR- and IR-monitored photolysis – or, what a difference a methyl makes","authors":"Simon J. George ,&nbsp;Aubrey D. Scott ,&nbsp;Leland B. Gee ,&nbsp;Lance C. Seefeldt ,&nbsp;Stephen P. Cramer","doi":"10.1016/j.jinorgbio.2025.113203","DOIUrl":"10.1016/j.jinorgbio.2025.113203","url":null,"abstract":"<div><div>A critical step in the global nitrogen cycle is the conversion of dinitrogen into biologically accessible ammonia. In Nature this is accomplished by the nitrogenase (N₂ase) family of enzymes. Carbon monoxide (CO) has long been known as an inhibitor of dinitrogen reduction by N₂ase, but it can also be a substrate of the enzyme, when it is catalytically reduced to hydrocarbons. Understanding the CO interactions with N₂ases are thus relevant to both dinitrogen fixation and Fischer-Tropsch-like chemistry. Here, the interaction of CO with the α-V70I variant of <em>Azotobacter vinelandii</em> MoFe N₂ase was investigated using electron paramagnetic resonance (EPR) and infrared (IR) monitored photolysis of bound CO under cryogenic conditions. This was supplemented by further analysis of stopped-flow Fourier transform IR (SF-FT-IR) data under turnover conditions. The α-V70I variant adds a single methyl group close to the FeMo-cofactor active site, and the results show that this inhibits and slows, but does not substantially chemically change, the binding of CO to the FeMo-cofactor. The EPR spectra of both the hi-CO and lo-CO states closely resemble those from the wild-type enzyme. Similarly, the SF-FT-IR spectra of CO inhibited α-V70I and wild-type enzyme are strikingly similar, showing only small shifts in band energies which allow better interpretation of the published wild-type spectra. The extra carbon does, however, impact and inhibit the photochemical release and migration of CO at cryogenic temperatures, resulting in novel CO-bound species. These include a product species, termed Lo-1*, which may involve CO photochemically migrating on the FeMo-cofactor.</div></div>","PeriodicalId":364,"journal":{"name":"Journal of Inorganic Biochemistry","volume":"277 ","pages":"Article 113203"},"PeriodicalIF":3.2,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The cobalamin-binding domain of cobalamin-dependent radical S-adenosylmethionine enzymes: Familiarity in unfamiliar places","authors":"Dante M. Avalos ,&nbsp;Catherine L. Drennan","doi":"10.1016/j.jinorgbio.2025.113204","DOIUrl":"10.1016/j.jinorgbio.2025.113204","url":null,"abstract":"<div><div>Cobalamin (Cbl)-dependent Radical <em>S</em>-adenosylmethionine (RS) enzymes are well known for their use of two powerful cofactors to catalyze chemically challenging reactions, such as methylations on unactivated carbons and phosphorus centers, ring contractions, ring formations, and thioether bond formations. Our repertoire of Cbl-dependent RS enzyme structures has grown since the first solved structure of the oxetanocin A biosynthetic enzyme OxsB in 2017, which has provided insight into the structural basis of catalysis. In particular, the Cbl-binding domains of these RS enzymes have been found to have interesting structural variations that seem to correlate with enzymatic function, at least for the small number of enzymes that have been characterized. In this review, we highlight the recent research about the Cbl cofactor in Cbl-dependent RS enzymes. We compare modes of Cbl binding and demonstrate a previously undetected connection between a subgroup of Cbl-dependent RS enzymes and the corrinoid iron‑sulfur protein (CFeSP) from the Wood-Ljungdahl pathway of reductive acetogenesis. Additionally, we discuss recent mechanistic findings on Cbl-dependent RS enzymes OxsB and its close homolog AlsB, which have not been recently reviewed. As Cbl-dependent RS enzymes are involved in making antiviral and antibiotic compounds, herbicides, and other molecules of value, understanding and manipulating enzyme activity has implications in both medicine and agriculture.</div></div>","PeriodicalId":364,"journal":{"name":"Journal of Inorganic Biochemistry","volume":"277 ","pages":"Article 113204"},"PeriodicalIF":3.2,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Polypyridyl Ru(II) tamoxifen analogues: Estrogen receptor-targeted dual photodynamic and chemotherapeutic agents","authors":"Guillermo Moreno-Alcántar ,&nbsp;Claudia Schmidt ,&nbsp;Darren Dennis Wragg ,&nbsp;Riccardo Scotti ,&nbsp;Iñigo Iribarren Aguirre ,&nbsp;Riccardo Bonsignore ,&nbsp;Angela Casini ,&nbsp;Denise Lovison","doi":"10.1016/j.jinorgbio.2025.113202","DOIUrl":"10.1016/j.jinorgbio.2025.113202","url":null,"abstract":"<div><div>The use of targeted chemotherapeutic agents and of locally active treatments such as photodynamic therapy (PDT), are strategies to tackle the side effects and enhance the effectiveness of anticancer treatments. In this context, the development of multifunctional drugs, which combine targeted chemotherapy and photosensitizing capabilities, has garnered increased attention. Herein, we introduce two polypyridyl ruthenium(II) compounds featuring tamoxifen-related ligands (<strong>RuTamOMe</strong> and <strong>RuTamOH</strong>) targeting the estrogen receptor α (ERα) and able to generate singlet oxygen via energy transfer. The compounds display enhanced phototoxicity, tested in different cell lines (A375 melanoma, MDA-MB-231 triple negative adenocarcinoma and MCF-7 ER+ breast cancer cells) and examined in terms of the ERα expression dependence. Computational studies were also performed, corroborating the suitability of the compounds to target ER, maintaining tamoxifen's affinity for the receptor binding site, and revealing a minimal influence of the stereochemical configuration of the compounds on their targeting capabilities. Altogether, our results highlight the potential of <em>hybrid</em> Ru(II) polypyridyl compounds as suitable platforms for generating targeted metallodrugs with photosensitizing capabilities.</div></div>","PeriodicalId":364,"journal":{"name":"Journal of Inorganic Biochemistry","volume":"277 ","pages":"Article 113202"},"PeriodicalIF":3.2,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145802189","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spectroscopic characterization of Mn2+-induced catalysis in cyclic GMP-AMP synthase","authors":"Karis Williamson,&nbsp;Karina Sharafutdinova,&nbsp;Micah Gaddy,&nbsp;Lucy Jolley,&nbsp;Parker Tamucci,&nbsp;Jaren Lobb,&nbsp;Eleana Parks,&nbsp;Noah Griffin,&nbsp;Molly M. Lockart","doi":"10.1016/j.jinorgbio.2025.113200","DOIUrl":"10.1016/j.jinorgbio.2025.113200","url":null,"abstract":"<div><div>Cyclic GMP-AMP synthase (cGAS) is a nucleotidyltransferase enzyme that functions as the principal cytosolic sensor of double-stranded DNA (dsDNA) in vertebrates. Upon binding dsDNA, cGAS produces the second messenger 2′3′-cyclic GMP-AMP (2′3′-cGAMP), initiating innate immune signaling. Canonical models describe activation through dsDNA-induced dimerization and recruitment of two Mg²⁺ ions into the active site. Recent studies, however, have identified Mn²⁺ as an alternative cofactor that accelerates catalysis, enhances substrate selectivity, and improves product fidelity. Interestingly, in the presence of dsDNA, Mn²⁺ acts as the preferred catalytic metal, and in its absence, it can promote dsDNA-independent synthesis of 2′3′-cGAMP. The metal-dependent divergence in activity raises key questions about the composition of the active metal cluster and the molecular basis for catalytic enhancement. Here, liquid chromatography–tandem mass spectrometry (LC-MS/MS) and electron paramagnetic resonance (EPR) spectroscopy, including electron spin echo envelope modulation (ESEEM) and electron–nuclear double resonance (ENDOR), were used to probe Mn²⁺ coordination and its interaction with substrates. Mn²⁺–cGAS generated approximately sixfold more cGAMP than Mg²⁺–cGAS with dsDNA and fourteenfold more without dsDNA, confirming enhanced catalysis and dsDNA-independent activation. CW and pulsed EPR revealed that Mn²⁺ uptake occurs during active-site assembly and that Mn²⁺ is coordinated by ATP and protein-derived ligands in the substrate-bound complex. These results provide the first spectroscopic description of Mn²⁺ coordination in cGAS and offer critical mechanistic insight into its metal-dependent activation and broader role in health and disease. Additionally, this work further defines how metal cofactors regulate innate immune signaling by cGAS.</div></div>","PeriodicalId":364,"journal":{"name":"Journal of Inorganic Biochemistry","volume":"277 ","pages":"Article 113200"},"PeriodicalIF":3.2,"publicationDate":"2025-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145802165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"When the wrong metal stops the cycle: Dynamics and specificity in plant copper-dependent peptide cyclases","authors":"Courtney M. Petersen,&nbsp;Winston C. Pitts,&nbsp;Shabnam Hematian","doi":"10.1016/j.jinorgbio.2025.113201","DOIUrl":"10.1016/j.jinorgbio.2025.113201","url":null,"abstract":"<div><div>Herein, we report the expression of split BURP domain peptide cyclases (BpCs), primarily CamB1 from <em>Ceanothus americanus</em>, in <em>Escherichia coli</em> using the pET22b vector without a fusion partner while retaining their disordered N-terminal region. To our knowledge, this represents the first full-length split BpC expressed and isolated without reliance on a stabilizing fusion tag (<em>e.g.</em>, maltose binding protein, MBP). Both CamB1 and ArbB2, from <em>Coffea arabica</em>, were purified and refolded from inclusion bodies, and displayed robust catalytic turnover on a minimal peptide substrate. Copper titrations revealed that catalytic assays using glutathione as the reducing agent require copper far in excess of the stoichiometric number of active sites, with activity plateauing at ∼50-fold excess, likely reflecting competition with nonspecific copper binding or solution speciation. Using ascorbic acid in place of glutathione not only restores but also increases maximal activity, requiring only near-stochiometric copper. Metal impact studies demonstrated that noncognate metals inhibit activity. Zn(II) most severely inhibited BpC function at low micromolar concentrations in enzyme-initiated assays containing Cu(II), Zn(II), and glutathione, but this effect was markedly alleviated in reducing agent-initiated assays and instead resembled the modest inhibition by Ag(I), which fully suppressed activity only near 1 mM. These results highlight how assay order influences metal competition at the active site. Given that BURP-domain proteins are implicated in plant stress responses, including tolerance to metal exposure, these findings suggest that Zn(II) and Ag(I) inhibition may represent a biochemical mechanism by which environmental metal stress modulates BpC activity.</div></div>","PeriodicalId":364,"journal":{"name":"Journal of Inorganic Biochemistry","volume":"277 ","pages":"Article 113201"},"PeriodicalIF":3.2,"publicationDate":"2025-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"From single step hops to emergent biological phenomena","authors":"Andrew J. Smith ,&nbsp;Cadmus D. Chen ,&nbsp;Bochu Wang ,&nbsp;Xiao Huang ,&nbsp;Chenfengtao Zheng ,&nbsp;Youhyun Nam ,&nbsp;David N. Beratan","doi":"10.1016/j.jinorgbio.2025.113191","DOIUrl":"10.1016/j.jinorgbio.2025.113191","url":null,"abstract":"<div><div>Charge transfer and transport are fundamental to chemistry and biochemistry. Since the 1950s, theorists and experimentalists have advanced the field to develop a molecular-level understanding of single-electron/one-step electron transfer, and ongoing studies explore multi-step, multi-electron, and multi-particle transfer and transport. This review highlights studies from our group on electron transfer beyond the one-electron/one-step regime. In particular, we review progress on electron bifurcation reactions, ultra-long range hopping transport in cable bacteria and bacterial nanowires, oxidative damage pathways, and charge transport pathways in nucleic acids. We highlight emerging themes and mechanisms across biological structures, including the roles being discovered for electron-electron correlations, rapid long-range multi-step biological electron transport, unconventional charge transport pathways, and competing charge transfer mechanisms.</div></div>","PeriodicalId":364,"journal":{"name":"Journal of Inorganic Biochemistry","volume":"276 ","pages":"Article 113191"},"PeriodicalIF":3.2,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145786844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lactoperoxidase: Identification of the two Tyr radical sites for the stabilization of the pH-dependent [Fe(IV) = O Tyr•] catalytic intermediates by resonance Raman and multifrequency Electron Paramagnetic Resonance spectroscopies","authors":"Piotr J. Mak ,&nbsp;Sandra Acebes ,&nbsp;Victor Guallar ,&nbsp;James R. Kincaid ,&nbsp;Anabella Ivancich","doi":"10.1016/j.jinorgbio.2025.113199","DOIUrl":"10.1016/j.jinorgbio.2025.113199","url":null,"abstract":"<div><div>We have fully characterized the high-valent intermediates formed during the catalytic cycle of lactoperoxidase (LPO), a heme-containing enzyme present in milk, saliva, tears and airways, playing an important role in mammalian antimicrobial defense. Our combined approach of multifrequency (9–285 GHz) Electron Paramagnetic Resonance (EPR) and resonance Raman (rR) spectroscopies allowed the identification of Tyr21 and Tyr193 as radical sites, having a concerted role with the heme iron and resulting in two distinct [Fe(IV) = O Tyr^•] intermediates in LPO's catalytic cycle. The presence and strength of H-bonds to Tyr^• assessed by the C − O stretching mode (v_7a) and the gx component of the g-tensor detected in their rR and 285-GHz EPR spectra, respectively, induced a difference in pH-dependent stabilization of the [Fe(IV) = O Tyr₂₁^•] and [Fe(IV) = O Tyr₁₉₃^•] intermediates. The later resulted from single-step electron tunneling subsequent to the formation of the [Fe(IV) = O Por^•+] species. A Trp radical contributing to the LPO 285-GHz EPR spectra, discern by the advantageous resolution of g-values, is proposed to facilitate the electron transfer to Tyr193. Our computational analysis (PELE) crucially identified a unique surface binding site for 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), close to Tyr21 (shown to host the spin by QM/MM simulations), thus consistent with LPO Tyr^• pH 5.6 detected in the rR and 285-GHz EPR spectra and the substrate oxidation previously shown by our UV–Vis stopped flow electronic absorption studies. The elucidation of the catalytic electron transfer pathways and the protein-based oxidizing sites is relevant to harnessing the concerted reactivity of heme and specific Tyr/Trp sites in natural biocatalysts.</div></div>","PeriodicalId":364,"journal":{"name":"Journal of Inorganic Biochemistry","volume":"277 ","pages":"Article 113199"},"PeriodicalIF":3.2,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145839079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}