Dumont M E, Ernst J F, Hampsey D M, Sherman F
EMBO J. 1987 Jan;6(1):235-41. doi: 10.1002/j.1460-2075.1987.tb04744.x.
Mitochondrial cytochrome c contains a heme group covalently attached through thioether linkages to two cysteinyl residues of the protein. We demonstrate here that the nuclear gene, CYC3, in the yeast Saccharomyces cerevisiae, encodes cytochrome c heme lyase (CCHL), the enzyme catalyzing the attachment of heme to apocytochrome c. Mitochondrial extracts from cyc3- mutants are deficient in CCHL activity compared with extracts from normal strains, whereas strains carrying multiple copies of the CYC3 gene exhibit high levels of the activity. The CYC3 gene was cloned by functional complementation of a cyc3- mutant using a previously isolated plasmid containing the gene PYK1, which is tightly linked to CYC3. An open reading frame encoding a protein of 269 amino acids was identified from the DNA sequence of a fragment encompassing the CYC3 gene, and the corresponding transcript shown to be approximately 0.9 kb in length. CCHL appears to be a single polypeptide chain which acts specifically on the two forms of cytochrome c, but not on cytochrome c1.
线粒体细胞色素c含有一个通过硫醚键与该蛋白质的两个半胱氨酸残基共价连接的血红素基团。我们在此证明，酵母酿酒酵母中的核基因CYC3编码细胞色素c血红素连接酶（CCHL），该酶催化血红素与脱辅基细胞色素c的连接。与正常菌株的提取物相比，cyc3-突变体的线粒体提取物缺乏CCHL活性，而携带CYC3基因多个拷贝的菌株表现出高水平的该活性。通过使用先前分离的包含与CYC3紧密连锁的基因PYK1的质粒对cyc3-突变体进行功能互补，克隆了CYC3基因。从包含CYC3基因的片段的DNA序列中鉴定出一个编码269个氨基酸的蛋白质的开放阅读框，并且相应的转录本显示长度约为0.9 kb。CCHL似乎是一条单多肽链，它特异性作用于细胞色素c的两种形式，但不作用于细胞色素c1。
