title: Redox control of fast ligand dissociation from Escherichia coli cytochrome bd.
abstract: Bacterial bd-type quinol oxidases, such as cytochrome bd from Escherichia coli, contain three hemes, but no copper. In contrast to heme-copper oxidases and similarly to globins, single electron-reduced cytochrome bd forms stable complexes with O(2), NO and CO at ferrous heme d. Kinetics of ligand dissociation from heme d(2+) in the single electron- and fully-reduced cytochrome bd from E. coli has been investigated by rapid mixing spectrophotometry at 20 degrees C. Data show that (i) O(2) dissociates at 78 s(-1), (ii) NO and CO dissociation is fast as compared to heme-copper oxidases and (iii) dissociation in the single electron-reduced state is hindered as compared to the fully-reduced enzyme. Presumably, rapid ligand dissociation requires reduced heme b(595). As NO, an inhibitor of respiratory oxidases, is involved in the immune response against microbial infection, the rapid dissociation of NO from cytochrome bd may have important bearings on the patho-physiology of enterobacteria.
authors.affiliation: Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119992, Russian Federation.
authors.forename: Vitaliy B
authors.initials: VB
authors.lastname: Borisov
authors.forename: Elena
authors.initials: E
authors.lastname: Forte
authors.forename: Paolo
authors.initials: P
authors.lastname: Sarti
authors.forename: Maurizio
authors.initials: M
authors.lastname: Brunori
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Konstantinov
authors.forename: Alessandro
authors.initials: A
authors.lastname: Giuffrè
mesh_terms: D002248:Carbon Monoxide / Q000378:metabolism; D003573:Cytochrome b Group; D003580:Cytochromes / Q000302:isolation & purification / Q000378:metabolism*; D045222:Electron Transport Chain Complex Proteins / Q000302:isolation & purification / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000302:isolation & purification / Q000378:metabolism*; D006418:Heme / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D009569:Nitric Oxide / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000302:isolation & purification / Q000378:metabolism*; D010101:Oxygen Consumption; D011485:Protein Binding; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D003573:Cytochrome b Group; D003580:Cytochromes; D045222:Electron Transport Chain Complex Proteins; D029968:Escherichia coli Proteins; D008024:Ligands; D011994:Recombinant Proteins; D009569:Nitric Oxide; D006418:Heme; D002248:Carbon Monoxide; D010088:Oxidoreductases; C040077:cytochrome bd terminal oxidase complex, E coli