期刊
JOURNAL OF BIOCHEMISTRY
卷 153, 期 6, 页码 535-545出版社
OXFORD UNIV PRESS
DOI: 10.1093/jb/mvt019
关键词
cyanide-insensitive quinol oxidase (CIO); cytochrome bd; cytochrome bo(3); Gluconobacter oxydans; respiratory chain
资金
- Japan Society for the Promotion of Science [20658020, 22380054]
- Grants-in-Aid for Scientific Research [23580115, 20658020, 22380054] Funding Source: KAKEN
Cyanide-insensitive terminal quinol oxidase (CIO) is a subfamily of cytochrome bd present in bacterial respiratory chain. We purified CIO from the Gluconobacter oxydans membranes and characterized its properties. The air-oxidized CIO showed some or weak peaks of reduced haemes b and of oxygenated and ferric haeme d, differing from cytochrome bd. CO- and NO-binding difference spectra suggested that haeme d serves as the ligand-binding site of CIO. Notably, the purified CIO showed an extraordinary high ubiquinol-1 oxidase activity with the pH optimum of pH 5-6. The apparent V-max value of CIO was 17-fold higher than that of G. oxydans cytochrome bo(3). In addition, compared with Escherichia coli cytochrome bd, the quinol oxidase activity of CIO was much more resistant to cyanide, but sensitive to azide. The K-m value for O-2 of CIO was 7- to 10-fold larger than that of G. oxydans cytochrome bo(3) or E. coli cytochrome bd. Our results suggest that CIO has unique features attributable to the structure and properties of the O-2-binding site, and thus forms a new sub-group distinct from cytochrome bd. Furthermore, CIO of acetic acid bacteria may play some specific role for rapid oxidation of substrates under acidic growth conditions.
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