Svensson B, Lübben M, Hederstedt L
Department of Microbiology, Lund University, Sweden.
Mol Microbiol. 1993 Oct;10(1):193-201. doi: 10.1111/j.1365-2958.1993.tb00915.x.
Haem A, a prosthetic group of many respiratory oxidases, is probably synthesized from haem B (protohaem IX) in a pathway in which haem O is an intermediate. Possible roles of the Bacillus subtilis ctaA and ctaB gene products in haem O and haem A synthesis were studied. Escherichia coli does not contain haem A. The ctaA gene on plasmids in E. coli resulted in haem A accumulation in membranes. The presence of ctaB together with ctaA increased the amount of haem A found in E. coli. Haem O was not detected in wild-type B. subtilis strains. A previously isolated B. subtilis ctaA deletion mutant was found to contain haem B and haem O, but not haem A. B. subtilis ctaB deletion mutants were constructed and found to lack both haem A and haem O. The results with E. coli and B. subtilis strongly suggest that the B. subtilis CtaA protein functions in haem A synthesis. It is tentatively suggested that if functions in the oxygenation/oxidation of the methyl side group of carbon 8 of haem O. B. subtilis CtaB, which is homologous to Saccharomyces cerevisiae COX10 and E. coli CyoE, also has a role in haem A synthesis and seems to be required for both cytochrome a and cytochrome o synthesis.
血红素A是许多呼吸氧化酶的辅基，可能是由血红素B（原血红素IX）通过以血红素O为中间产物的途径合成的。对枯草芽孢杆菌ctaA和ctaB基因产物在血红素O和血红素A合成中的可能作用进行了研究。大肠杆菌不含血红素A。大肠杆菌质粒上的ctaA基因导致血红素A在膜中积累。ctaB与ctaA共同存在增加了大肠杆菌中血红素A的含量。在野生型枯草芽孢杆菌菌株中未检测到血红素O。发现先前分离的枯草芽孢杆菌ctaA缺失突变体含有血红素B和血红素O，但不含血红素A。构建了枯草芽孢杆菌ctaB缺失突变体，发现其既缺乏血红素A也缺乏血红素O。大肠杆菌和枯草芽孢杆菌的结果强烈表明，枯草芽孢杆菌CtaA蛋白在血红素A合成中起作用。初步推测它在血红素O的8位碳原子甲基侧链的氧合/氧化中起作用。与酿酒酵母COX10和大肠杆菌CyoE同源的枯草芽孢杆菌CtaB在血红素A合成中也有作用，似乎是细胞色素a和细胞色素o合成所必需的。
