A putative pathway for perosamine biosynthesis is the first function encoded within the rfb region of Vibrio cholerae O1.
The first four genes (rfbA,B,D,E) of the rfb region of Vibrio cholerae O1 are predicted to encode the enzymes required for the biosynthesis of perosamine, which constitutes the backbone structure of the O-antigen of the lipopolysaccharide. Based on homology to known proteins/protein families, the following functions are predicted: RfbA, phosphomannose isomerase-guanosine diphosphomannose pyrophosphorylase; RfbB, phosphomanno-mutase; RfbD, oxido reductase and RfbE, perosamine synthetase (amino-transferase). Thus, perosamine is synthesized from fructose 6-phosphate via the intermediates mannose 6-phosphate by RfbA, to mannose 1-phosphate by RfbB, to GDP-mannose by RfbA, to GDP-4-keto-6-dideoxymannose by RfbD and to GDP-perosamine by RfbE. This final product would then serve as the substrate for the addition of the tetronate, which could then be polymerized into the O-antigen for transfer to the lipid A plus core oligosaccharide and export to the cell surface. The organization of these genes are such that one would expect them to be translationally coupled as part of the rfb operon. However, the absence of readily detectable promoter sequences suggests low levels of transcription, in line with other studies. The nucleotide sequence of these genes is absolutely conserved in the two isolates 569B (classical, Inaba) and O17 (El Tor, Ogawa) which were expected to show maximal sequence variation. This suggests very tight constraints on the micro-evolution within these sequences.
Department of Microbiology and Immunology, University of Adelaide, Australia.
U H
UH
Stroeher
L E
LE
Karageorgos
M H
MH
Brown
R
R
Morona
P A
PA
Manning
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D001665:Binding Sites; D002238:Carbohydrate Epimerases / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D006836:Hydro-Lyases / Q000235:genetics / Q000378:metabolism; D008358:Mannose / Q000031:analogs & derivatives* / Q000096:biosynthesis; D008359:Mannose-6-Phosphate Isomerase / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism; D019081:O Antigens / Q000096:biosynthesis*; D009876:Operon; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D017875:Phosphotransferases (Phosphomutases) / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry; D012045:Regulatory Sequences, Nucleic Acid; D015183:Restriction Mapping; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D000637:Transaminases / Q000235:genetics / Q000378:metabolism; D014734:Vibrio cholerae / Q000201:enzymology / Q000235:genetics / Q000276:immunology*; D002237:Carbohydrate Dehydrogenases
D001426:Bacterial Proteins; D002238:Carbohydrate Epimerases; D004269:DNA, Bacterial; D006836:Hydro-Lyases; D008358:Mannose; D008359:Mannose-6-Phosphate Isomerase; D009097:Multienzyme Complexes; D009713:Nucleotidyltransferases; D019081:O Antigens; D010088:Oxidoreductases; D017875:Phosphotransferases (Phosphomutases); D011994:Recombinant Proteins; D000637:Transaminases; C080207:phosphomannose isomerase-guanosine diphospho-D-mannose pyrophosphorylase; C057033:4-amino-4,6-dideoxy-D-mannose; C085243:dTDP-D-glucose synthase; C022771:dTDPglucose 4,6-dehydratase; C061272:perosamine synthetase; C020092:dTDP-4-ketorhamnose 3,5-epimerase; D002237:Carbohydrate Dehydrogenases; C052799:phosphomannomutase