title: Importance of hydrophobic interaction between a SoxB-type cytochrome c oxidase with its natural substrate cytochrome c-551 and its mutants.
abstract: Cytochrome c-551, the electron donor of SoxB-type cytochrome c oxidase in thermophilic bacilli, can be over-expressed in Bacillus thermodenitrificans cells by tranformation with pSTEc551. Several mutant cytochromes c-551 were prepared by site-directed mutagenesis to this expression plasmid. Among them, several Lys residues were changed to Ala/Ser, and we found that these mutant cytochromes retained their activity as substrates, although their K(m) values were 0.04-0.12 microM, depending on the site replaced. In contrast, the C19A mutant cytochrome, which was produced in Brevibacillus choshinensis as a secretion protein, lost its activity as a substrate, suggesting that the fatty acyl-glyceryl residue covalently bound to the cysteine residue of the wild-type c-551 plays a very important role in the activity. The importance of the hydrophobic fatty acid residue for the binding of cytochrome c-551 to the oxidase was also shown by the loss of substrate activity in deacylated cytochrome c-551. These results show the importance of the hydrophobic interaction between this cytochrome and SoxB-type oxidase, despite the fact that the importance of an electrostatic interaction between cytochrome c and mitochondrial cytochrome aa(3) oxidase has already been established.
authors.affiliation: Department of Biochemical Engineering and Science, Kyushu Institute of Technology, Kawazu, Iizuka, Fukuoka 820-8502, Japan.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Kagekawa
authors.forename: Makoto
authors.initials: M
authors.lastname: Mizukami
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Noguchi
authors.forename: Junshi
authors.initials: J
authors.lastname: Sakamoto
authors.forename: Nobuhito
authors.initials: N
authors.lastname: Sone
mesh_terms: D000595:Amino Acid Sequence; D001407:Bacillus / Q000201:enzymology / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D003574:Cytochrome c Group / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D001426:Bacterial Proteins; D003574:Cytochrome c Group; D005227:Fatty Acids; D007506:Iron-Sulfur Proteins; D009097:Multienzyme Complexes; C017167:cytochrome C(551); D010088:Oxidoreductases; C064500:flavocytochrome c sulfide dehydrogenase