A cb-type cytochrome-c oxidase terminates the respiratory chain in Helicobacter pylori.
A Helicobacter pylori membrane fraction oxidized yeast and equine cytochrome c, and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD). When ascorbate was used as reductant, the Vmax and apparent Km values were 612 nmol electron min-1 (mg protein)-1 and 14 microM for yeast, and 419 nmol electron min-1 (mg protein)-1 and 19 microM for equine cytochrome c, respectively. For TMPD oxidation, the Vmax and Km values were 640 nmol electron min-1 (mg protein)-1 and 182 microM, respectively. These oxidase activities showed a high affinity for oxygen. Inhibition of both cytochrome-c and TMPD oxidase activities by 50% was caused by about 4 microM cyanide and about 0.5 mM azide. Redox difference spectra of the membrane solubilized with Triton X-100 showed b- or c-type cytochromes but not aa3-type cytochromes. c-type and a part of some b-type cytochromes were reduced with ascorbate plus TMPD. A CO difference spectrum revealed that protohaem, but not an aa3-type cytochrome, may be interacting with CO/oxygen. Only protohaem was detected in the haem fraction extracted from the membrane. Three polypeptides (60, 38 and 29 kDa) were found to be bearing haem c after SDS-PAGE of the membrane. From these results, it was suggested that the cbb3-type cytochrome-c oxidase, having a haem-copper binuclear centre like the cytochrome aa3-type oxidase, but differing in a few other properties, functions as a terminal oxidase in the respiratory chain of H. pylori.
Nagata
K
K
Department of Bacteriology, Hyogo College of Medicine, Nishinomiya, Japan.
Tsukita
S
S
Tamura
T
T
Sone
N
N
D000818:Animals; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism*; D016480:Helicobacter pylori / Q000378:metabolism*; D006418:Heme / Q000737:chemistry; D006736:Horses; D066298:In Vitro Techniques; D007700:Kinetics; D008566:Membranes / Q000378:metabolism; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D013053:Spectrophotometry; D013772:Tetramethylphenylenediamine / Q000378:metabolism
D006418:Heme; D003576:Electron Transport Complex IV; D013772:Tetramethylphenylenediamine