title: Nano-mechanical mapping of the interactions between surface-bound RC-LH1-PufX core complexes and cytochrome c 2 attached to an AFM probe.
abstract: Electron transfer pathways in photosynthesis involve interactions between membrane-bound complexes such as reaction centres with an extrinsic partner. In this study, the biological specificity of electron transfer between the reaction centre-light-harvesting 1-PufX complex and its extrinsic electron donor, cytochrome c 2, formed the basis for mapping the location of surface-attached RC-LH1-PufX complexes using atomic force microscopy (AFM). This nano-mechanical mapping method used an AFM probe functionalised with cyt c 2 molecules to quantify the interaction forces involved, at the single-molecule level under native conditions. With surface-bound RC-His12-LH1-PufX complexes in the photo-oxidised state, the mean interaction force with cyt c 2 is approximately 480 pN with an interaction frequency of around 66 %. The latter value lowered 5.5-fold when chemically reduced RC-His12-LH1-PufX complexes are imaged in the dark to abolish electron transfer from cyt c 2 to the RC. The correspondence between topographic and adhesion images recorded over the same area of the sample shows that affinity-based AFM methods are a useful tool when topology alone is insufficient for spatially locating proteins at the surface of photosynthetic membranes.
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK, c.vasilev@sheffield.ac.uk.
authors.forename: Cvetelin
authors.initials: C
authors.lastname: Vasilev
authors.forename: Amanda A
authors.initials: AA
authors.lastname: Brindley
authors.forename: John D
authors.initials: JD
authors.lastname: Olsen
authors.forename: Rafael G
authors.initials: RG
authors.lastname: Saer
authors.forename: J T
authors.initials: JT
authors.lastname: Beatty
authors.forename: C N
authors.initials: CN
authors.lastname: Hunter
mesh_terms: D045362:Cytochromes c2 / Q000378:metabolism*; D004579:Electron Transport / Q000502:physiology; D018625:Microscopy, Atomic Force; D008954:Models, Biological; D010788:Photosynthesis / Q000502:physiology*; D012242:Rhodobacter sphaeroides / Q000378:metabolism
chemical_list: D045362:Cytochromes c2
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