title: The cps gene cluster of Salmonella strain LT2 includes a second mannose pathway: sequence of two genes and relationship to genes in the rfb gene cluster.
abstract: We report the presence in Salmonella enterica strain LT2 (serovar thyphimurium) of duplicate genes for two steps in the synthesis of GDP-mannose. The previously known genes, rfbK (phosphomannomutase) and rfbM (mannose-1-phosphate guanyltransferase), are part of the gene cluster for the O antigen. The two new genes, cpsB and cpsG, respectively, are thought to be part of the gene cluster for the M antigen capsular polysaccharide, present in many Enterobacteriaceae. The two genes have been sequenced and have a GC content of 0.61, suggesting an origin outside of Salmonella. Comparison of the inferred protein sequences for cpsB and rfbM shows 57% identity of amino acids whereas for cpsG and rfbK there is only 19% identity. It is suggested that the greater divergence between cpsG and rfbK may be due to a period of accelerated evolution, perhaps precipitated by transfer of the genes from another species.
authors.affiliation: Department of Microbiology, University of Sydney, N.S.W., Australia.
authors.forename: G
authors.initials: G
authors.lastname: Stevenson
authors.forename: S J
authors.initials: SJ
authors.lastname: Lee
authors.forename: L K
authors.initials: LK
authors.lastname: Romana
authors.forename: P R
authors.initials: PR
authors.lastname: Reeves
mesh_terms: D000595:Amino Acid Sequence; D001482:Base Composition; D001483:Base Sequence; D003001:Cloning, Molecular; D005787:Gene Frequency; D006155:Guanosine Diphosphate Mannose / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics; D007535:Isomerases / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family; D009713:Nucleotidyltransferases / Q000235:genetics*; D017875:Phosphotransferases (Phosphomutases); D011135:Polysaccharides, Bacterial; D012475:Salmonella / Q000201:enzymology / Q000235:genetics* / Q000276:immunology; D012689:Sequence Homology, Nucleic Acid
chemical_list: D007527:Isoenzymes; D011135:Polysaccharides, Bacterial; D006155:Guanosine Diphosphate Mannose; D009713:Nucleotidyltransferases; C021546:mannose-1-phosphate guanylyltransferase (GDP); D007535:Isomerases; D017875:Phosphotransferases (Phosphomutases); C052799:phosphomannomutase