title: A Brownian dynamics study of the interactions of the luminal domains of the cytochrome b6f complex with plastocyanin and cytochrome c6: the effects of the Rieske FeS protein on the interactions.
abstract: The availability of the structures of the cytochrome b6f complex (cyt b6f), plastocyanin (PC), and cytochrome c6 (cyt c6) from Chlamydomonas reinhardtii allowed us, for the first time, to model electron transfer interactions between the luminal domains of this complex (including cyt f and the Rieske FeS protein) and its redox partners in the same species. We also generated a model structure in which the FeS center of the Rieske protein was positioned closer to the heme of cyt f than observed in the crystal structure and studied its interactions with both PC and cyt c6. Our data showed that the Rieske protein in both the original crystal structure and in our modeled structure of the cyt b6f complex did not physically interfere with binding position or orientation of PC or cyt c6 on cyt f. PC docked on cyt f with the same orientation in the presence or the absence of the Rieske protein, which matched well with the previously reported NMR structures of complexes between cyt f and PC. When the FeS center of the Rieske protein was moved close to the heme of cyt f, it even enhanced the interaction rates. Studies using a cyt f modified in the 184-191 loop showed that the cyt f structure is a more important factor in determining the rate of complex formations than is the presence or the absence of the Rieske protein or its position with respect to cyt f.
authors.affiliation: Biophysics Program and Department of Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Esmael J
authors.initials: EJ
authors.lastname: Haddadian
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Gross
mesh_terms: D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000737:chemistry*; D003198:Computer Simulation; D045346:Cytochrome b6f Complex / Q000737:chemistry*; D045365:Cytochromes c6 / Q000737:chemistry*; D045348:Cytochromes f / Q000737:chemistry; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010970:Plastocyanin / Q000737:chemistry*; D011485:Protein Binding
chemical_list: D045365:Cytochromes c6; D007506:Iron-Sulfur Proteins; C037989:Rieske iron-sulfur protein; D010970:Plastocyanin; D045346:Cytochrome b6f Complex; D045348:Cytochromes f; D014450:Electron Transport Complex III