棒子结束操纵子:证据表明过去基因(cobT)低配体的催化合成维生素B12, dimethylbenzimidazole。
文章的细节
-
引用
复制到剪贴板 -
陈P, Ailion M,韦安德一道N,罗斯J
棒子结束操纵子:证据表明过去基因(cobT)低配体的催化合成维生素B12, dimethylbenzimidazole。
J Bacteriol。1995年3月,177 (6):1461 - 9。
- PubMed ID
-
7883701 (在PubMed]
- 文摘
-
鼠伤寒沙门氏菌包括20个基因的玉米操纵子致力于合成adenosyl-cobalamin(辅酶B12)。突变体的病变promoter-distal操纵子的合成维生素B12只有提供5,6-dimethylbenzimidazole (DMB),维生素B12的低配体。希望确定一个基因参与DMB的合成(s)的DNA碱基序列的操纵子已经确定;这就完成了棒子的操纵子序列。cobT基因是基因操纵子。四个CobII (DMB)映射到不同的缺失突变CobII地区测序的时间间隔;所有影响cobT开放阅读框。美国沙门氏菌感染和假单胞菌的CobT蛋白质相同器官已被证明在体外从烟酸酯催化磷酸核糖转移单核苷酸DMB。这个反应并不导致DMB合成而是第一步加入DMB科林环化合物cobinamide。因此,沙门氏菌cobT突变体的表型冲突的报道活动受影响的酶,而假单胞菌突变体预期表型。 J. R. Trzebiatowski, G. A. O'Toole, and J. C. Escalante Semerena have suggested (J. Bacteriol. 176:3568-3575, 1994) that S. typhimurium possesses a second phosphoribosyltransferase activity (CobB) that requires a high concentration of DMB for its activity. We support that suggestion and, in addition, provide evidence that the CobT protein catalyzes both the synthesis of DMB and transfer of ribose phosphate. Some cobT mutants appear defective only in DMB synthesis, since they grow on low levels of DMB and retain their CobII phenotype in the presence of a cobB mutation. Other mutants including those with deletions, appear defective in transferase, since they require a high level of DMB (to activate CobB) and, in combination with a cobB mutation, they eliminate the ability to join DMB and cobinamide. Immediately downstream of the cob operon is a gene (called ORF in this study) of unknown function whose mutants have no detected phenotype. Just counterclockwise of ORF is an asparagine tRNA gene (probably asnU). Farther counterclockwise, a serine tRNA gene (serU or supD) is weakly cotransducible with the cobT gene.