Marsh E N, McKie N, Davis N K, Leadlay P F
Department of Biochemistry, University of Cambridge, U.K.
Biochem J. 1989 Jun 1;260(2):345-52. doi: 10.1042/bj2600345.
The structural genes coding for both subunits of adenosylcobalamin-dependent methylmalonyl-CoA mutase from the Gram-positive bacterium Propionibacterium shermanii have been cloned, with the use of synthetic oligonucleotides as primary hybridization probes. The genes are closely linked and are transcribed in the same direction. Nucleotide sequence analysis of 4.5 kb of DNA encompassing both genes allowed us to infer the complete amino acid sequence of the two subunits: the beta-subunit is the product of the upstream gene, and consists of 638 amino acid residues (Mr 69465) and the alpha-subunit consists of 728 amino acid residues (Mr 80,147). There is a very close structural homology between the two subunits, reflecting the probable duplication of a common ancestral gene. A sequence present only in the alpha-subunit is significantly homologous to a portion of the sequence of the methylmalonyl-CoA-binding subunit of transcarboxylase from P. shermanii [Samols, Thornton, Murtif, Kumar, Haase & Wood (1988) J. Biol. Chem. 263, 6461-6464], and this homologous region may form part of the CoA ester-binding site in both enzymes.
利用合成寡核苷酸作为初次杂交探针，已克隆出革兰氏阳性细菌谢氏丙酸杆菌中编码腺苷钴胺素依赖性甲基丙二酰辅酶A变位酶两个亚基的结构基因。这些基因紧密相连且转录方向相同。对包含这两个基因的4.5 kb DNA进行核苷酸序列分析，使我们能够推断出这两个亚基的完整氨基酸序列：β亚基是上游基因的产物，由638个氨基酸残基组成（Mr 69465），α亚基由728个氨基酸残基组成（Mr 80,147）。两个亚基之间存在非常紧密的结构同源性，这反映了一个共同祖先基因可能发生了重复。仅存在于α亚基中的一个序列与谢氏丙酸杆菌转羧酶的甲基丙二酰辅酶A结合亚基的部分序列具有显著同源性[萨莫尔斯、桑顿、默蒂夫、库马尔、哈泽和伍德（1988年）《生物化学杂志》263, 6461 - 6464]，并且这个同源区域可能在两种酶中都构成辅酶A酯结合位点的一部分。
