title: Unanswered questions about the structure of cytochrome bc1 complexes.
abstract: X-ray crystal structures of bc1 complexes obtained over the last 15 years have provided a firm structural basis for our understanding of the complex. For the most part there is good agreement between structures from different species, different crystal forms, and with different inhibitors bound. In this review we focus on some of the remaining unexplained differences, either between the structures themselves or the interpretations of the structural observations. These include the structural basis for the motion of the Rieske iron-sulfur protein in response to inhibitors, a possible conformational change involving tyrosine132 of cytochrome (cyt) b, the presence of cis-peptides at the beginnings of transmembrane helices C, E, and H, the structural insight into the function of the so-called "Core proteins", different modelings of the retained signal peptide, orientation of the low-potential heme b, and chirality of the Met ligand to heme c1. This article is part of a Special Issue entitled: Respiratory complex III and related bc complexes.
authors.affiliation: Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA. Electronic address: BerryE@upstate.edu.
authors.forename: Edward A
authors.initials: EA
authors.lastname: Berry
authors.forename: Heather
authors.initials: H
authors.lastname: De Bari
authors.forename: Li-Shar
authors.initials: LS
authors.lastname: Huang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D014450:Electron Transport Complex III / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006418:Heme / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D021122:Protein Subunits; D006418:Heme; D014450:Electron Transport Complex III
keywords: ASU; Complex III; E(m); Heme orientation; Heme protein; IC(50); ISP; MIP; MPP; Matrix processing peptidase; NCS; Non-pro cis peptide; PDB; Q(P), Q(N); Rieske iron-sulfur protein; Ubiquinol:cytochrome c reductase; alkylhydroxydioxobenzothiazole; asymmetric unit; cyt; cytochrome; inhibitor concentration giving 50% inhibition; iron–sulfur protein; matrix intermediate peptidase; matrix processing peptidase of mitochondria; nHDBT; noncrystallographic symmetry; pH dependent standard reduction potential E′°; protein databank; quinone processing active sites of the bc complex near the negative (–) and positive (Q(P)) surfaces of the energy transducing membrane