Biochimica et Biophysica Acta-Bioenergetics最新文献

Ischemia-reperfusion (IR) injury remains a major contributor to organ dysfunction following transient ischemic insults. Although numerous interventions have been found effective to reduce IR injury in preclinical models, none of these therapies have been successfully translated to the clinical setting. In the context of the persistent translational gap, we systematically investigated the mechanisms implicated in IR injury using kidney donation and transplantation as a clinical model of IR. Whilst our results do not implicate traditional culprits such as reactive oxygen species, complement activation or inflammation as triggers of IR injury, they reveal a clear metabolic signature for renal IR injury. This discriminatory signature of IR injury is consistent with a post-reperfusion metabolic paralysis and involves high-energy phosphate depletion, tricarboxylic acid cycle defects, and a compensatory activation of catabolic routes. Against this background, the picture emerges that clinical IR injury is driven by reductive stress. In this article, we therefore wish to elaborate on the processes contributing to reductive stress in the context of clinical IR injury and provide a better insight in potential clinical therapeutic strategies that might be helpful in restoring the redox balance.

To professional bioenergeticists, the thermodynamic and kinetic constraints on mitochondrial function are self-evident. It is therefore profoundly concerning that high-profile cell biology papers continue to appear containing fundamental bioenergetic errors that appear to have evaded the scrutiny of the principal investigator, co-authors, editors and, apparently, at least some of the referees. The problem is not new, and seems to stem from a perception that bioenergetics is a 'difficult' subject, both at undergraduate level, if it is taught in any depth, and in research, where cell biologists are faced with biophysical concepts such as protonmotive force, ion flux, redox potential and Gibbs free energy.

The human mitochondrial nicotinamide nucleotide transhydrogenase (NNT) uses the proton motive force to drive hydride transfer from NADH to NADP⁺ and is a major contributor to the generation of mitochondrial NADPH. NNT plays a critical role in maintaining cellular redox balance. NNT-deficiency results in oxidative damage and its absence results in familial glucocorticoid deficiency. Recently it has also become clear that NNT is a tumor promoter whose presence in mouse models of non-small cell lung cancer results in enhanced tumor growth and aggressiveness. The presence of NNT mitigates the effects of oxidative stress and facilitates cancer cell proliferation, suggesting NNT-inhibition as a promising therapeutic strategy. The human NNT is a homodimer in which each subunit has a molecular weight of 114 kDa and 14 transmembrane spans. Here we report on the development of a system for isolating full-length recombinant human NNT using Escherichia coli. The purified enzyme is catalytically active, and the enzyme reconstituted into proteoliposomes pumps protons and generates a proton motive force capable of driving ATP synthesis by E. coli ATP synthase. The recombinant human NNT will facilitate structural and biochemical studies as well as provide a useful tool to develop and characterize potential anti-cancer therapeutics.

In this study, the oligomerization pattern of apo- and holoforms of the Orange Carotenoid Protein (OCP) was examined under different conditions such as photoactivation state, concentration, and carotenoid embedment using analytical ultracentrifugation. Furthermore, studies were conducted on OCP constructs carrying point mutations of amino acid residues affecting OCP oligomerization. Our findings reveal that the concentration-dependent dimerization of dark-adapted OCP holoprotein from Synechocystis sp. PCC 6803 can be effectively prevented by the R27L mutation in the OCP-NTD. By introducing the E258R mutation (also in conjunction with R27L) into the OCP-CTD, monomeric OCP apoprotein can be obtained. Additionally, the holoprotein of the dark-adapted OCP-R27L/E258R variant was monomeric, and, supported by size-exclusion chromatography experiments, the photoactivated form of the OCP-R27L/E258R variant was monomeric as well. This variant, which does not oligomerize in either photocycle state, returns from the photoactivated to the dark-adapted state at a significantly faster rate than the OCP wild-type and the R27L mutant thereof. These observations also highlight the crucial interdependence between OCP dimerization in both photocycle states, the lifetime of the photoactive state of OCP, and the kinetics of the OCP photocycle.

The F₁ domain of F_oF₁-ATP synthases/ATPases (F_oF₁) possesses three catalytic sites on the three αβ interfaces, termed α_Eβ_E, α_Dβ_D, and α_Tβ_T, located mainly on the β subunits. The enzyme also has three non-catalytic ATP-binding sites on the three αβ interfaces, located mainly on the α subunits. When ATP does not bind to the non-catalytic site, F_oF₁ becomes significantly prone to ADP inhibition, ultimately resulting in the loss of ATPase activity. However, the underlying mechanism of ADP inhibition remains unclear. Here, we report the cryo-EM structure of the non-catalytic site-depleted (ΔNC) F_oF₁ from thermophilic Bacillus sp. PS-3, which completely lacks the ability to bind ATP (and ADP) upon transitioning to the ADP-inhibited form. The structure closely resembled the 81° rotated structure of the wild-type F_oF₁, except for minor movements in the C-terminal region of the α subunit. In this structure, unlike the wild-type enzyme, the catalytic site at α_Dβ_D, responsible for ATP hydrolysis, was occupied by ADP-Mg, with the absence of Pi. Furthermore, the catalytic site at α_Eβ_E, where ATP enters the F₁ domain during steady-state catalysis, is occupied by ADP, seemingly impeding further ATP binding to the enzyme. The structure suggests that the ADP-inhibited form of the F₁ domain is more likely due to differences in the nucleotide-binding states at the catalytic sites rather than structural differences.

Mitochondrial dysfunction and increased reactive oxygen species (ROS) generation play an import role in different human pathologies. In this context, mitochondrial targeting of potentially protective antioxidants by their coupling to the lipophilic triphenylphosphonium cation (TPP) is widely applied. Employing a six‑carbon (C₆) linker, we recently demonstrated that mitochondria-targeted phenolic antioxidants derived from gallic acid (AntiOxBEN₂) and caffeic acid (AntiOxCIN₄) counterbalance oxidative stress in primary human skin fibroblasts by activating ROS-protective mechanisms. Here we demonstrate that C₆-TPP (but not AntiOxBEN₂ and AntiOxCIN₄) induce cell death in human skin fibroblasts. This indicates that C₆-TPP cytoxocity is counterbalanced by the antioxidant moieties of AntiOxBEN₂ and AntiOxCIN₄. Remarkably, C₆-TPP and AntiOxBEN₂ (but not AntiOxCIN₄) induced a glycolytic switch, as exemplified by a reduced cellular oxygen consumption rate (OCR), increased extracellular acidification rate (ECAR), elevated extracellular lactate levels, and higher protein levels of glucose transporter 1 (GLUT-1). This switch involved activation of AMP-activated protein kinase (AMPK) and fully compensated for the loss in mitochondrial ATP production by sustaining cellular ATP content. When glycolytic switch induction was prevented (i.e. by using a glucose-free, galactose-containing medium), AntiOxBEN₂ induced cell death whereas AntiOxCIN₄ did not. We conclude that, despite their similar chemical structure and antioxidant capacity, AntiOxBEN₂ and AntiOxCIN₄ display both common (redox-adaptive) and specific (bioenergetic-adaptive) effects.

The reduction of oxygen to water is crucial to life under aerobic conditions. Cytochrome bd oxidases perform this reaction with a very high oxygen affinity. Members of this protein family are solely found in prokaryotes and some archaea playing an important role in bacterial virulence and antibiotic resistance. Here, we combine mutagenesis, electrocatalysis, nitric oxide binding and release experiments as well as FTIR spectroscopy to demonstrate that proton delivery to the active site is essentially rate limiting in Cyt bd-I electrocatalysis. D58 and D105 of subunit CydB are crucial residues in this proton path and communicate via a hydrogen bond network. Oxygen reduction depends on proton delivery to the active site, which also influences NO release.

Advancements in materials science, synthetic biology, and nanomaterial engineering are revolutionizing renewable energy technologies, creating new pathways for sustainable energy production. Biohybrid devices-systems combining biological components with engineered synthetic materials-are emerging as powerful platforms for harnessing solar energy to drive hydrogen production, photovoltaics, catalysis, and biosensing. This collection of articles presents leading-edge research in biohybrid energy systems, where photosynthetic mechanisms are redeployed to develop eco-friendly, high-efficiency alternatives to conventional solar technologies. Central to these biohybrid designs are diverse organisms, from cyanobacteria and algae to purple bacteria and archaea, enabling researchers to employ a broad range of bioengineered proteins and photosynthetic complexes. By integrating advances in synthetic biology with precision nanomaterial fabrication, scientists can improve protein functionality and device stability at the nanoscale, optimizing these systems for light absorption, energy conversion, and resilience. This convergence allows exploring unique photoactive pigments, including type I and type II reaction centers, specialized light-harvesting and retinal-binding proteins. Through protein engineering and careful selection of photoactive components, biohybrid devices offer promising solutions for sustainable energy applications, positioning photosynthetic organisms as critical contributors to innovative energy technology.

The Publisher regrets that this article is an accidental duplication of an article that has already been published, https://doi.org/10.1016/j.bbabio.2024.149534. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/policies/article-withdrawal.