Single-Molecule Detection of the Encounter and Productive Electron Transfer Complexes of a Photosynthetic Reaction Center

作者：Cvetelin Vasilev, Jon Nguyen, Adam G.M. Bowie, Guy E. Mayneord, Elizabeth C. Martin, Andrew Hitchcock, Taras V. Pogorelov, Abhishek Singharoy, C. Neil Hunter, Matthew P. Johnson · 发表于：Journal of the American Chemical Society · 年份：2024 · DOI：10.1021/jacs.4c03913 · 被引用次数：8 · 研究领域：Photosynthetic Processes and Mechanisms、Electrochemical Analysis and Applications、ATP Synthase and ATPases Research

High Resolution Image Download MS PowerPoint Slide Small, diffusible redox proteins play an essential role in electron transfer (ET) in respiration and photosynthesis, sustaining life on Earth by shuttling electrons between membrane-bound complexes via finely tuned and reversible interactions. Ensemble kinetic studies show transient ET complexes form in two distinct stages: an “encounter” complex largely mediated by electrostatic interactions, which subsequently, through subtle reorganization of the binding interface, forms a “productive” ET complex stabilized by additional hydrophobic interactions around the redox-active cofactors. Here, using single-molecule force spectroscopy (SMFS) we dissected the transient ET complexes formed between the photosynthetic reaction center-light harvesting complex 1 (RC-LH1) of Rhodobacter sphaeroides and its native electron donor cytochrome c 2 (cyt c 2 ). Importantly, SMFS resolves the distribution of interaction forces into low (∼150 pN) and high (∼330 pN) components, with the former more susceptible to salt concentration and to alteration of key charged residues on the RC. Thus, the low force component is suggested to reflect the contribution of electrostatic interactions in forming the initial encounter complex, whereas the high force component reflects the additional stabilization provided by hydrophobic interactions to the productive ET complex. Employing molecular dynamics simulations, we resolve five intermediate states that compris...