Single-molecule study of redox control involved in establishing the spinach plastocyanin-cytochrome b6f electron transfer complex

Publication date: Available online 24 June 2019Source: Biochimica et Biophysica Acta (BBA) - BioenergeticsAuthor(s): Guy E. Mayneord, Cvetelin Vasilev, Lorna A. Malone, David J.K. Swainsbury, C. Neil Hunter, Matthew P. JohnsonAbstractSmall diffusible redox proteins play a ubiquitous role in bioenergetic systems, facilitating electron transfer (ET) between membrane bound complexes. Sustaining high ET turnover rates requires that the association between extrinsic and membrane-bound partners is highly specific, yet also sufficiently weak to promote rapid post-ET separation. In oxygenic photosynthesis the small soluble electron carrier protein plastocyanin (Pc) shuttles electrons between the membrane integral cytochrome b6f (cytb6f) and photosystem I (PSI) complexes. Here we use peak-force quantitative nanomechanical mapping (PF-QNM) atomic force microscopy (AFM) to quantify the dynamic forces involved in transient interactions between cognate ET partners. An AFM probe functionalised with Pc molecules is brought into contact with cytb6f complexes, immobilised on a planar silicon surface. PF-QNM interrogates the unbinding force of the cytb6f-Pc interactions at the single molecule level with picoNewton force resolution and on a time scale comparable to the ET time in vivo (ca. 120 μs). Using this approach, we show that although the unbinding force remains unchanged the interaction frequency increases over five-fold when Pc and cytb6f are in opposite redox states, so complementar...
Source: Biochimica et Biophysica Acta (BBA) Bioenergetics - Category: Biochemistry Source Type: research