title: Identification of a fourth gene involved in dTDP-rhamnose synthesis in Streptococcus mutans.
abstract: 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.
authors.affiliation: Department of Preventive Dentistry, Kyushu University Faculty of Dentistry, Fukuoka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Tsukioka
authors.forename: Y
authors.initials: Y
authors.lastname: Yamashita
authors.forename: Y
authors.initials: Y
authors.lastname: Nakano
authors.forename: T
authors.initials: T
authors.lastname: Oho
authors.forename: T
authors.initials: T
authors.lastname: Koga
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002237:Carbohydrate Dehydrogenases / Q000235:genetics*; D004269:DNA, Bacterial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics*; D009702:Nucleoside Diphosphate Sugars / Q000096:biosynthesis*; D011817:Rabbits; D013295:Streptococcus mutans / Q000201:enzymology* / Q000235:genetics; D013942:Thymine Nucleotides / Q000096:biosynthesis*
chemical_list: D004269:DNA, Bacterial; D009097:Multienzyme Complexes; D009702:Nucleoside Diphosphate Sugars; D013942:Thymine Nucleotides; C073293:thymidine diphosphate rhamnose; D002237:Carbohydrate Dehydrogenases; C107144:dTDP-4-dehydrorhamnose reductase