Tsukioka Y, Yamashita Y, Nakano Y, Oho T, Koga T
Department of Preventive Dentistry, Kyushu University Faculty of Dentistry, Fukuoka, Japan.
J Bacteriol. 1997 Jul;179(13):4411-4. doi: 10.1128/jb.179.13.4411-4414.1997.
We had isolated three genes (rmlA, rmlB, and rmlC) involved in dTDP-rhamnose synthesis in Streptococcus mutans and found that three genes were insufficient for dTDP-rhamnose synthesis (Y. Tsukioka, Y. Yamashita, T. Oho, Y. Nakano, and T. Koga, J. Bacteriol. 179:1126-1134, 1997). The rmlD gene of S. mutans, encoding the enzyme which catalyzes the last step of dTDP-rhamnose synthesis, has been cloned and sequenced. The cell extract of Escherichia coli expressing the rmlD gene of S. mutans exhibited enzymatic activity corresponding to its counterpart in Shigella flexneri, a gram-negative bacterium. Rhamnose was not detected in the cell wall preparation purified from the mutant in which the cloned gene was insertionally inactivated. Rabbit antiserum against S. mutans serotype c-specific antigen did not react with autoclaved extracts from the mutant. The rmlD gene product of S. mutans compensated for the incompleteness of dTDP-rhamnose synthesis by the three previously isolated genes. These results indicate that the rmlD gene product is indispensable for the dTDP-rhamnose pathway and subsequently for the synthesis of serotype-specific antigen in S. mutans. Furthermore, conservation of the rmlD gene in Streptococcus species was demonstrated by Southern blot analysis.
我们已经分离出了变形链球菌中参与dTDP - 鼠李糖合成的三个基因（rmlA、rmlB和rmlC），并且发现这三个基因对于dTDP - 鼠李糖合成是不充分的（Y. Tsukioka、Y. Yamashita、T. Oho、Y. Nakano和T. Koga，《细菌学杂志》179:1126 - 1134，1997年）。变形链球菌的rmlD基因已被克隆并测序，该基因编码催化dTDP - 鼠李糖合成最后一步的酶。表达变形链球菌rmlD基因的大肠杆菌细胞提取物表现出与革兰氏阴性菌弗氏志贺菌中对应酶相当的酶活性。在从克隆基因插入失活的突变体中纯化的细胞壁制剂中未检测到鼠李糖。抗变形链球菌c型特异性抗原的兔抗血清不与该突变体的高压灭菌提取物发生反应。变形链球菌的rmlD基因产物弥补了先前分离的三个基因在dTDP - 鼠李糖合成方面的不完整性。这些结果表明，rmlD基因产物对于dTDP - 鼠李糖途径以及随后变形链球菌中血清型特异性抗原的合成是必不可少的。此外，通过Southern印迹分析证明了rmlD基因在链球菌属中的保守性。
