title: Analysis of the structures of the subunits of the cytochrome bc1 complex from beef heart mitochondria.
abstract: The interaction of the protein subunits of the bc1 complex from beef heart is analysed on the basis of protein chemical data and of secondary structure predictions suggesting a large number of amphipathic helices. Electrostatic interactions, i.e. helix-dipole interactions and ionic bonds, may play a major role in the stabilisation of the arrangement of the subunits within the multi-protein complex, formation of subcomplexes and maintenance of the steric strain of cytochrome b. A model of the heme-carrying 'core' of cytochrome b, i.e. of helices II-V, is presented consisting of a twisted '4-alpha-helical' bundle held together by helix-dipole interactions and stabilised by the interaction with other protein subunits of the bc1 complex.
mesh_terms: D000818:Animals; D002417:Cattle; D004578:Electron Spin Resonance Spectroscopy; D014450:Electron Transport Complex III; D006418:Heme / Q000378:metabolism; D046911:Macromolecular Substances; D008929:Mitochondria, Heart / Q000201:enzymology*; D008968:Molecular Conformation; D009097:Multienzyme Complexes / Q000032:analysis*; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011808:Quinone Reductases / Q000032:analysis*
chemical_list: D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D006418:Heme; D011808:Quinone Reductases; D014450:Electron Transport Complex III