Novel insights into the mechanism of electron transfer in mitochondrial cytochrome c

Pérez‐Mejías, Gonzalo; Díaz-Quintana, Antonio; Guerra‐Castellano, Alejandra; Dı́az-Moreno, Irene; Rosa, Miguel Á. De la

doi:10.1016/j.ccr.2021.214233

Cited by 19 publications

(17 citation statements)

References 135 publications

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“…the type of contacts between PSI and Pc. Thus, we hypothesize that Mg 2+ screens specific electrostatic interactions involved in binding (complex formation), water interactions, and/or the establishment of a Gouy–Chapman conduit, ,, and that this effect is independent of illumination. Unfortunately, binding forces cannot be directly measured with SMFS, and although association constants k on have been reported from AFM-SMFS measurements, these calculations are challenging and require multiple assumptions …”

Section: Resultsmentioning

confidence: 99%

“…In plants, plastocyanin (Pc) is the small water-soluble copper-containing redox protein responsible for shuttling electrons between cytochrome b6f complex (Cyt b6f ) and the photosystem I (PSI). The effective encounter of Pc with PSI and Cyt b6f is determined by transient and specific interactions . The transient nature of the complex formed between PSI and Pc in the PETC implies a balance between specificity and binding strength.…”

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confidence: 99%

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Light- and Redox-Dependent Force Spectroscopy Reveals that the Interaction between Plastocyanin and Plant Photosystem I Is Favored when One Partner Is Ready for Electron Transfer

et al. 2022

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Photosynthesis is a fundamental process that converts photons into chemical energy, driven by large protein complexes at the thylakoid membranes of plants, cyanobacteria, and algae. In plants, water-soluble plastocyanin (Pc) is responsible for shuttling electrons between cytochrome b6f complex and the photosystem I (PSI) complex in the photosynthetic electron transport chain (PETC). For an efficient turnover, a transient complex must form between PSI and Pc in the PETC, which implies a balance between specificity and binding strength. Here, we studied the binding frequency and the unbinding force between suitably oriented plant PSI and Pc under redox control using single molecule force spectroscopy (SMFS). The binding frequency (observation of binding-unbinding events) between PSI and Pc depends on their respective redox states. The interaction between PSI and Pc is independent of the redox state of PSI when Pc is reduced, and it is disfavored in the dark (reduced P700) when Pc is oxidized. The frequency of interaction between PSI and Pc is higher when at least one of the partners is in a redox state ready for electron transfer (ET), and the post-ET situation (PSIRed-PcOx) leads to lower binding. In addition, we show that the binding of ET-ready PcRed to PSI can be regulated externally by Mg2+ ions in solution.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Light- and Redox-Dependent Force Spectroscopy Reveals that the Interaction between Plastocyanin and Plant Photosystem I Is Favored when One Partner Is Ready for Electron Transfer

et al. 2022

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“…Our recent observation of inter-protein long-distance ET between C c 1 and C c through the aqueous solution 4 can be explained by the presence of a charge conduit at the active interface between the two proteins (Gouy-Chapman conduit). These results suggest that ET could occur already when the two proteins are approaching (i.e., in the encounter state) without the need of establishing a well-defined, static protein complex, thereby reconciling high specificity with weak binding, and allowing to keep the high turnover rate required in the ETC 5 . Within this scenario, the presence of a charge conduit is of paramount importance for a sustained electron transport.…”

Section: Introductionmentioning

confidence: 91%

“…The recent direct experimental observation of electrochemically gated, long-distance ET between cytochrome c 1 (C c 1 , subunit of the cytochrome bc 1 ) and C c through the aqueous solution suggested that such tradeoff is achieved without direct contact, by molding the ionic distribution and electric field between their redox-active sites 4 . Thus, these redox protein partners might conciliate high specificity with weak binding, to keep the high turnover rate required by their biological function 5 .…”

Section: Introductionmentioning

confidence: 99%

Phosphorylation disrupts long-distance electron transport in cytochrome c

et al. 2022

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It has been recently shown that electron transfer between mitochondrial cytochrome c and the cytochrome c1 subunit of the cytochrome bc1 can proceed at long-distance through the aqueous solution. Cytochrome c is thought to adjust its activity by changing the affinity for its partners via Tyr48 phosphorylation, but it is unknown how it impacts the nanoscopic environment, interaction forces, and long-range electron transfer. Here, we constrain the orientation and separation between cytochrome c1 and cytochrome c or the phosphomimetic Y48pCMF cytochrome c, and deploy an array of single-molecule, bulk, and computational methods to investigate the molecular mechanism of electron transfer regulation by cytochrome c phosphorylation. We demonstrate that phosphorylation impairs long-range electron transfer, shortens the long-distance charge conduit between the partners, strengthens their interaction, and departs it from equilibrium. These results unveil a nanoscopic view of the interaction between redox protein partners in electron transport chains and its mechanisms of regulation.

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“…We mimic the interprotein ET-like situation facing protein partners bound to electrodes and located at nanometer proximity. , In this configuration, for a redox cognate pair of the respiratory chain, we measured current at distances as long as 12 nm through the aqueous solution. , Furthermore, the spatial span of the interprotein current in cytochrome c is regulated by phosphorylation, which highlights the biological relevance of this observation. In the absence of a redox chain in the electrolyte solution, such observations require a different mechanism than ET in the bound complex, raising several questions: can the ETp mechanisms operating in the polypeptide structures support charge transport between proteins through the solution? are observations of long-distance currents restricted to these cytochrome partners or is it a general phenomenon?…”

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confidence: 99%

The Protein Matrix of Plastocyanin Supports Long-Distance Charge Transport with Photosystem I and the Copper Ion Regulates Its Spatial Span and Conductance

López-Ortiz,

Zamora,

Giannotti

et al. 2023

ACS Nano

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Charge exchange is the fundamental process that sustains cellular respiration and photosynthesis by shuttling electrons in a cascade of electron transfer (ET) steps between redox cofactors. While intraprotein charge exchange is well characterized in protein complexes bearing multiple redox sites, interprotein processes are less understood due to the lack of suitable experimental approaches and the dynamic nature of the interactions. Proteins constrained between electrodes are known to support electron transport (ETp) through the protein matrix even without redox cofactors, as the charges housed by the redox sites in ET are furnished by the electrodes. However, it is unknown whether protein ETp mechanisms apply to the interprotein medium present under physiological conditions. We study interprotein charge exchange between plant photosystem I (PSI) and its soluble redox partner plastocyanin (Pc) and address the role of the Pc copper center. Using electrochemical scanning tunneling spectroscopy (ECSTS) current−distance and blinking measurements, we quantify the spatial span of charge exchange between individual Pc/PSI pairs and ETp through transient Pc/PSI complexes. Pc devoid of the redox center (Pc apo ) can exchange charge with PSI at longer distances than with the copper ion (Pc holo ). Conductance bursts associated with Pc apo /PSI complex formation are higher than in Pc holo /PSI. Thus, copper ions are not required for long-distance Pc/PSI ETp but regulate its spatial span and conductance. Our results suggest that the redox center that carries the charge in Pc is not necessary to exchange it in interprotein ET through the aqueous solution and question the canonical view of tight complex binding between redox protein partners.

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Novel insights into the mechanism of electron transfer in mitochondrial cytochrome c

Cited by 19 publications

References 135 publications

Light- and Redox-Dependent Force Spectroscopy Reveals that the Interaction between Plastocyanin and Plant Photosystem I Is Favored when One Partner Is Ready for Electron Transfer

Light- and Redox-Dependent Force Spectroscopy Reveals that the Interaction between Plastocyanin and Plant Photosystem I Is Favored when One Partner Is Ready for Electron Transfer

Phosphorylation disrupts long-distance electron transport in cytochrome c

The Protein Matrix of Plastocyanin Supports Long-Distance Charge Transport with Photosystem I and the Copper Ion Regulates Its Spatial Span and Conductance

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