Oxygen reactivity of both respiratory oxidases in Campylobacter jejuni: the cydAB genes encode a cyanide-resistant, low-affinity oxidase that is not of the cytochrome bd type.
J Bacteriol
; 189(5): 1604-15, 2007 Mar.
Article
em En
| MEDLINE
| ID: mdl-17172349
ABSTRACT
The microaerophilic bacterium Campylobacter jejuni is a significant food-borne pathogen and is predicted to possess two terminal respiratory oxidases with unknown properties. Inspection of the genome reveals an operon (cydAB) apparently encoding a cytochrome bd-like oxidase homologous to oxidases in Escherichia coli and Azotobacter vinelandii. However, C. jejuni cells lacked all spectral signals characteristic of the high-spin hemes b and d of these oxidases. Mutation of the cydAB operon of C. jejuni did not have a significant effect on growth, but the mutation reduced formate respiration and the viability of cells cultured in 5% oxygen. Since cyanide resistance of respiration was diminished in the mutant, we propose that C. jejuni CydAB be renamed CioAB (cyanide-insensitive oxidase), as in Pseudomonas aeruginosa. We measured the oxygen affinity of each oxidase, using a highly sensitive assay that exploits globin deoxygenation during respiration-catalyzed oxygen uptake. The CioAB-type oxidase exhibited a relatively low affinity for oxygen (K(m) = 0.8 microM) and a V(max) of >20 nmol/mg/s. Expression of cioAB was elevated fivefold in cells grown at higher rates of oxygen provision. The alternative, ccoNOQP-encoded cyanide-sensitive oxidase, expected to encode a cytochrome cb'-type enzyme, plays a major role in the microaerobic respiration of C. jejuni, since it appeared to be essential for viability and exhibited a much higher oxygen affinity, with a K(m) value of 40 nM and a V(max) of 6 to 9 nmol/mg/s. Low-temperature photodissociation spectrophotometry revealed that neither oxidase has ligand-binding activity typical of the heme-copper oxidase family. These data are consistent with cytochrome oxidation during photolysis at low temperatures.
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1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Consumo de Oxigênio
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Campylobacter jejuni
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Cianetos
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Citocromos
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Complexo de Proteínas da Cadeia de Transporte de Elétrons
Tipo de estudo:
Prognostic_studies
Idioma:
En
Ano de publicação:
2007
Tipo de documento:
Article