Bengtsson Jenny, von Wachenfeldt Claes, Winstedt Lena, Nygaard Per, Hederstedt Lars
Department of Cell and Organism Biology, Lund University, Sölvegatan 35, SE-22362 Lund, Sweden.
Department of Biological Chemistry, University of Copenhagen, Solvgade 83, DK-1307 Copenhagen K, Denmark.
Microbiology (Reading). 2004 Feb;150(Pt 2):415-425. doi: 10.1099/mic.0.26691-0.
The Gram-positive bacterium Bacillus subtilis contains two respiratory oxidases of the haem-copper superfamily: cytochrome aa(3), which is a quinol oxidase, and cytochrome caa(3), which is a cytochrome c oxidase. Cytochrome c oxidase uniquely contains a di-copper centre, Cu(A). B. subtilis CtaG is a membrane protein encoded by the same gene cluster as that which encodes the subunits of cytochrome c oxidase. The role of B. subtilis CtaG and orthologous proteins present in many other Gram-positive bacteria has remained unexplored. The sequence of CtaG is unrelated to that of CtaG/Cox11p of proteobacteria and eukaryotic cells. This study shows that B. subtilis CtaG is essential for the formation of active cytochrome caa(3) but is not required for assembly of the core subunits I and II with haem in the membrane and it has no role in the synthesis of active cytochrome aa(3). B. subtilis YpmQ, a homologue to Sco1p of eukaryotic cells, is also a membrane-bound cytochrome c oxidase-specific assembly factor. Properties of CtaG- and YpmQ-deficient mutants were compared. Cells lacking YpmQ showed a low cytochrome c oxidase activity and this defect was suppressed by the supplementation of the growth medium with copper ions. It has previously been proposed that YpmQ/Sco1p is involved in synthesis of the Cu(A) centre. The results of this study are consistent with this proposal but the exact role of YpmQ in assembly of cytochrome c oxidase remains to be elucidated.
革兰氏阳性细菌枯草芽孢杆菌含有两种血红素-铜超家族的呼吸氧化酶：细胞色素aa(3)，它是一种喹啉氧化酶；以及细胞色素caa(3)，它是一种细胞色素c氧化酶。细胞色素c氧化酶独特地含有一个二铜中心，即Cu(A)。枯草芽孢杆菌CtaG是一种膜蛋白，其编码基因簇与编码细胞色素c氧化酶亚基的基因簇相同。枯草芽孢杆菌CtaG以及许多其他革兰氏阳性细菌中存在的直系同源蛋白的作用尚未得到探索。CtaG的序列与变形菌和真核细胞的CtaG/Cox11p的序列无关。本研究表明，枯草芽孢杆菌CtaG对于活性细胞色素caa(3)的形成至关重要，但对于核心亚基I和II与膜中的血红素组装不是必需的，并且它在活性细胞色素aa(3)的合成中没有作用。枯草芽孢杆菌YpmQ是真核细胞Sco1p的同源物，也是一种膜结合的细胞色素c氧化酶特异性组装因子。比较了缺乏CtaG和YpmQ的突变体的特性。缺乏YpmQ的细胞显示出低细胞色素c氧化酶活性，并且通过在生长培养基中补充铜离子可以抑制这种缺陷。以前有人提出YpmQ/Sco1p参与Cu(A)中心的合成。本研究结果与这一观点一致，但YpmQ在细胞色素c氧化酶组装中的具体作用仍有待阐明。
