Raux E, Lanois A, Warren M J, Rambach A, Thermes C
Department of Molecular Genetics, Institute of Ophthalmology, UCL, 11-43 Bath Street, London EC1V 9EL, UK.
Biochem J. 1998 Oct 1;335 ( Pt 1)(Pt 1):159-66. doi: 10.1042/bj3350159.
A 16 kb DNA fragment has been isolated from a Bacillus megaterium genomic library and fully sequenced. The fragment contains 15 open reading frames, 14 of which are thought to constitute a B. megaterium cobalamin biosynthetic (cob) operon. Within the operon, 11 genes display similarity to previously identified Salmonella typhimurium cobalamin biosynthetic genes (cbiH60, -J, -C, -D, -ET, -L, -F, -G, -A, cysGA and btuR), whereas three do not (cbiW, -X and -Y). The genes of the B. megaterium cob operon were compared with the cobalamin biosynthetic genes of Pseudomonas denitrificans, Methanococcus jannaschii and Synechocystis sp. Taking into account the presence of cbiD and cbiG, the absence of a cobF, cobG and cobN, -S and -T, it was concluded that B. megaterium, M. jannaschii and Synechocystis sp., like S. typhimurium, synthesize cobalamin by an anaerobic pathway, in which cobalt is added at an early stage and molecular oxygen is not required.
从巨大芽孢杆菌基因组文库中分离出一个16 kb的DNA片段并进行了全序列测定。该片段包含15个开放阅读框，其中14个被认为构成巨大芽孢杆菌钴胺素生物合成（cob）操纵子。在该操纵子内，11个基因与先前鉴定的鼠伤寒沙门氏菌钴胺素生物合成基因（cbiH60、-J、-C、-D、-ET、-L、-F、-G、-A、cysGA和btuR）相似，而另外三个则不相似（cbiW、-X和-Y）。将巨大芽孢杆菌cob操纵子的基因与反硝化假单胞菌、詹氏甲烷球菌和聚球藻属的钴胺素生物合成基因进行了比较。考虑到cbiD和cbiG的存在，以及cobF、cobG和cobN、-S和-T的缺失，得出结论：巨大芽孢杆菌、詹氏甲烷球菌和聚球藻属与鼠伤寒沙门氏菌一样，通过厌氧途径合成钴胺素，在该途径中，钴在早期添加，不需要分子氧。
