title: Structure of complex III with bound cytochrome c in reduced state and definition of a minimal core interface for electron transfer.
abstract: In cellular respiration, cytochrome c transfers electrons from cytochrome bc(1) complex (complex III) to cytochrome c oxidase by transiently binding to the membrane proteins. Here, we report the structure of isoform-1 cytochrome c bound to cytochrome bc(1) complex at 1.9 A resolution in reduced state. The dimer structure is asymmetric. Monovalent cytochrome c binding is correlated with conformational changes of the Rieske head domain and subunit QCR6p and with a higher number of interfacial water molecules bound to cytochrome c(1). Pronounced hydration and a "mobility mismatch" at the interface with disordered charged residues on the cytochrome c side are favorable for transient binding. Within the hydrophobic interface, a minimal core was identified by comparison with the novel structure of the complex with bound isoform-2 cytochrome c. Four core interactions encircle the heme cofactors surrounded by variable interactions. The core interface may be a feature to gain specificity for formation of the reactive complex.
authors.affiliation: Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany.
authors.forename: Sozanne R N
authors.initials: SR
authors.lastname: Solmaz
authors.forename: Carola
authors.initials: C
authors.lastname: Hunte
mesh_terms: D018360:Crystallography, X-Ray; D045304:Cytochromes c / Q000737:chemistry; D019281:Dimerization; D014450:Electron Transport Complex III / Q000737:chemistry*; D003576:Electron Transport Complex IV / Q000378:metabolism*; D004583:Electrons; D006860:Hydrogen Bonding; D008954:Models, Biological; D008958:Models, Molecular; D008968:Molecular Conformation; D011487:Protein Conformation; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013696:Temperature
chemical_list: D020033:Protein Isoforms; D045304:Cytochromes c; D003576:Electron Transport Complex IV; D014450:Electron Transport Complex III