Hu W, De Smet L, Van Driessche G, Bartsch R G, Meyer T E, Cusanovich M A, Van Beeumen J
Department of Biochemistry, Physiology and Microbiology, University of Gent, Belgium.
Eur J Biochem. 1998 Nov 15;258(1):29-36. doi: 10.1046/j.1432-1327.1998.2580029.x.
A cytochrome c-556 was purified from Rhodobacter capsulatus and the complete amino acid sequence was determined. It contains 328 amino acid residues and two typical heme-binding sites at cysteine residues 54 and 57 and at residues 200 and 203. It is homologous to the family of bacterial cytochrome c peroxidases (BCCP) with 69% identity to Paracoccus denitrificans BCCP and 60% identity to Pseudomonas aeruginosa BCCP for which there is a three-dimensional structure. There is lesser similarity to the mauG gene products from methylotrophic bacteria which are thought to be involved in biosynthesis of the quinone cofactor of methylamine dehydrogenase. Translated genes from Escherichia coli and Helicobacter pylori are also related to the bacterial cytochrome c peroxidases. The divergence of this family of proteins is reflected in the fact that the reported sixth heme ligands are not conserved, except in Pseudomonas, Rhodobacter and Paracoccus. This suggests that homologs of BCCP may fold differently and/or may not have the same enzymatic activity as the prototypic protein from Ps. aeruginosa. We found that the Rb. capsulatus BCCP is active with both Rb. capsulatus cytochrome c2 and with horse cytochrome c as substrates (Km values 60 microm and 6 microm, respectively). The turnover number was 40 s(-1) and the Km for peroxide was 33 microm. We have thus confirmed that the Rb. capsulatus protein is a cytochrome c peroxidase.
从荚膜红细菌中纯化出一种细胞色素c-556，并测定了其完整的氨基酸序列。它含有328个氨基酸残基，在半胱氨酸残基54和57以及残基200和203处有两个典型的血红素结合位点。它与细菌细胞色素c过氧化物酶（BCCP）家族同源，与反硝化副球菌BCCP的同一性为69%，与具有三维结构的铜绿假单胞菌BCCP的同一性为60%。与甲基营养细菌的mauG基因产物的相似性较小，后者被认为参与甲胺脱氢酶醌辅因子的生物合成。来自大肠杆菌和幽门螺杆菌的翻译基因也与细菌细胞色素c过氧化物酶有关。该蛋白质家族的差异反映在以下事实上：除了假单胞菌属（Pseudomonas）、红细菌属（Rhodobacter）和副球菌属（Paracoccus）外，报道的第六个血红素配体并不保守。这表明BCCP的同源物可能折叠方式不同和/或可能不具有与铜绿假单胞菌原型蛋白相同的酶活性。我们发现，荚膜红细菌BCCP以荚膜红细菌细胞色素c2和马细胞色素c作为底物时均具有活性（Km值分别为60微摩尔和6微摩尔）。周转数为40 s(-1)，过氧化物的Km为33微摩尔。因此，我们证实了荚膜红细菌蛋白是一种细胞色素c过氧化物酶。
