title: Identification of amino acid residues essential for reconstitutive activity of subunit IV of the cytochrome bc1 complex from Rhodobacter sphaeroides.
abstract: A region of subunit IV comprising residues 77-85 is identified as essential for interaction with the core complex to restore the bc(1) activity (reconstitutive activity). Recombinant subunit IV mutants with single or multiple alanine substitution at this region were generated and characterized to identify the essential amino acid residues. Residues 81-84, with sequence of YRYR, are required for reconstitutive activity of subunit IV, because a mutant with these four residues substituted with alanine has little activity, while a mutant with alanine substitution at residues 77-80 and 85 have the same reconstitutive activity as that of the wild-type IV. The positively charged group at R-82 and R-84 and both the hydroxyl group and aromatic group at Y-81 and Y-83 are essential. The interactions between these four residues of subunit IV and residues of core subunits are also responsible for the stability of the complex. However, these interactions are not essential for the incorporation of subunit IV into the bc(1) complex.
authors.affiliation: Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA.
authors.forename: Shih-Chia
authors.initials: SC
authors.lastname: Tso
authors.forename: Ying
authors.initials: Y
authors.lastname: Yin
authors.forename: Chang-An
authors.initials: CA
authors.lastname: Yu
authors.forename: Linda
authors.initials: L
authors.lastname: Yu
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D020134:Catalytic Domain / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D014450:Electron Transport Complex III / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012242:Rhodobacter sphaeroides / Q000201:enzymology* / Q000235:genetics; D013816:Thermodynamics
chemical_list: D004269:DNA, Bacterial; D021122:Protein Subunits; D011994:Recombinant Proteins; D014450:Electron Transport Complex III