Toledo-Cuevas M, Barquera B, Gennis R B, Wikström M, García-Horsman J A
Depàrtamento de Bioquímica, UNAM, Ciudad Universitaria, Mexico D.F., Mexico.
Biochim Biophys Acta. 1998 Jul 20;1365(3):421-34. doi: 10.1016/s0005-2728(98)00095-4.
Rhodobacter sphaeroides expresses a bb3-type quinol oxidase, and two cytochrome c oxidases: cytochrome aa3 and cytochrome cbb3. We report here the characterization of the genes encoding this latter oxidase. The ccoNOQP gene cluster of R. sphaeroides contains four open reading frames with high similarity to all ccoNOQP/fixNOQP gene clusters reported so far. CcoN has the six highly conserved histidines proposed to be involved in binding the low spin heme, and the binuclear center metals. ccoO and ccoP code for membrane bound mono- and diheme cytochromes c. ccoQ codes for a small hydrophobic protein of unknown function. Upstream from the cluster there is a conserved Fnr/FixK-like box which may regulate its expression. Analysis of a R. sphaeroides mutant in which the ccoNOQP gene cluster was inactivated confirms that this cluster encodes the cbb3-type oxidase previously purified. Analysis of proton translocation in several strains shows that cytochrome cbb3 is a proton pump. We also conclude that cytochromes cbb3 and aa3 are the only cytochrome c oxidases in the respiratory chain of R. sphaeroides.
球形红杆菌表达一种bb3型喹啉氧化酶以及两种细胞色素c氧化酶：细胞色素aa3和细胞色素cbb3。我们在此报告编码后一种氧化酶的基因的特性。球形红杆菌的ccoNOQP基因簇包含四个开放阅读框，与迄今报道的所有ccoNOQP/fixNOQP基因簇具有高度相似性。CcoN具有六个高度保守的组氨酸，推测其参与低自旋血红素以及双核中心金属的结合。ccoO和ccoP编码膜结合的单血红素和双血红素细胞色素c。ccoQ编码一种功能未知的小疏水蛋白。在该基因簇上游有一个保守的Fnr/FixK样框，可能调控其表达。对ccoNOQP基因簇失活的球形红杆菌突变体的分析证实，该基因簇编码先前纯化得到的cbb3型氧化酶。对多个菌株中质子转运的分析表明，细胞色素cbb3是一种质子泵。我们还得出结论，细胞色素cbb3和aa3是球形红杆菌呼吸链中仅有的细胞色素c氧化酶。
