title: Expression and characterization of the diheme cytochrome c subunit of the cytochrome bc complex in Heliobacterium modesticaldum.
abstract: Heliobacterium modesticaldum is a Gram-positive, anaerobic, anoxygenic photoheterotrophic bacterium. Its cytochrome bc complex (Rieske/cyt b complex) has some similarities to cytochrome b(6)f complexes from cyanobacteria and chloroplasts, and also shares some characteristics of typical bacterial cytochrome bc(1) complexes. One of the unique factors of the heliobacterial cytochrome bc complex is the presence of a diheme cytochrome c instead of the monoheme cytochrome f in the cytochrome b(6)f complex or the monoheme cytochrome c(1) in the bc(1) complex. To understand the structure and function of this diheme cytochrome c protein, we expressed the N-terminal transmembrane-helix-truncated soluble H. modesticaldum diheme cytochrome c in Escherichia coli. This 25kDa recombinant protein possesses two c-type hemes, confirmed by mass spectrometry and a variety of biochemical techniques. Sequence analysis of the H. modesticaldum diheme cytochrome c indicates that it may have originated from gene duplication and subsequent gene fusion, as in cytochrome c(4) proteins. The recombinant protein exhibits a single redox midpoint potential of +71mV versus NHE, which indicates that the two hemes have very similar protein environments.
authors: Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA.
authors: Hai
authors: H
authors: Yue
authors: Yisheng
authors: Y
authors: Kang
authors: Hao
authors: H
authors: Zhang
authors: Xinliu
authors: X
authors: Gao
authors: Robert E
authors: RE
authors: Blankenship
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D020440:Gene Duplication; D005798:Genes, Bacterial; D006094:Gram-Positive Bacteria / Q000235:genetics / Q000378:metabolism*; D006418:Heme / Q000737:chemistry; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D001426:Bacterial Proteins; D021122:Protein Subunits; D011994:Recombinant Proteins; D006418:Heme; D010088:Oxidoreductases; C090099:diheme cytochrome c