Taxonomic group: bacteria / Proteobacteria
(Phylum: Proteobacteria)
Associated disease: infection due to Escherichia coli [ICD11:
XN6P4 
]
NCBI PubMed ID: 7536735Publication DOI: 10.1128/jb.177.8.2178-2187.1995Journal NLM ID: 2985120RPublisher: American Society for Microbiology
Institutions: Max-Planck-Institute für Immunobiologie, Freiburg, Germany
The rfb gene cluster of Escherichia coli O9 directs the synthesis of the O9-specific polysaccharide which has the structure →2-α-Man-(1→2)-α-Man-(1→2)-α-Man-(1→3)-α-Man-(1→. The E. coli O9 rfb cluster has been sequenced, and six genes, in addition to the previously described rfbK and rfbM, were identified. They correspond to six open reading frames (ORFs) encoding polypeptides of 261, 431, 708, 815, 381, and 274 amino acids. They are all transcribed in the counter direction to those of the his operon. No gene was found between rfb and his. A higher G+C content indicated that E. coli O9 rfb evolved independently of the rfb clusters from other E. coli strains and from Shigella and Salmonella spp. Deletion mutagenesis, in combination with analysis of the in vitro synthesis of the O9 mannan in membranes isolated from the mutants, showed that three genes (termed mtfA, -B, and -C, encoding polypeptides of 815, 381, and 274 amino acids, respectively) directed α-mannosyl transferases. MtfC (from ORF274), the first mannosyl transferase, transfers a mannose to the endogenous acceptor. It critically depended on a functional rfe gene (which directs the synthesis of the endogenous acceptor) and initiates the growth of the polysaccharide chain. MtfB (from ORF381) then transfers two mannoses into the 3 position of the previous mannose, and MtfA (from ORF815) transfers three mannoses into the 2 position. Further chain growth needs only the two transferases MtfA and MtfB. Thus, there are fewer transferases needed than the number of sugars in the repeating unit. Analysis of the predicted amino acid sequence of the ORF261 and ORF431 proteins indicated that they function as components of an ATP-binding cassette transport system. A possible correlation between the mechanism of polymerization and mode of membrane translocation of the products is discussed.
biosynthesis, expression, gene, characterization, polysaccharide, O-antigen, Escherichia, Escherichia coli, rfb, transferase, cluster, gene cluster, sequencing, rfb gene cluster, Mannose, mannan, transport, transferases
Structure type: polymer chemical repeating unit
Location inside paper: Abstract
Trivial name: mannose homopolysaccharide
Compound class: O-polysaccharide, O-antigen
Contained glycoepitopes: IEDB_115576,IEDB_130701,IEDB_136104,IEDB_140116,IEDB_141111,IEDB_141795,IEDB_141830,IEDB_143632,IEDB_144983,IEDB_152206,IEDB_153756,IEDB_164174,IEDB_164175,IEDB_164176,IEDB_164480,IEDB_174840,IEDB_241100,IEDB_76933,IEDB_983930,SB_136,SB_196,SB_197,SB_44,SB_67,SB_72
Methods: DNA techniques
Comments, role: published polymerization frame was shifted for conformity with other records.
Related record ID(s): 5762, 7199, 10527, 20624, 25215
NCBI Taxonomy refs (TaxIDs): 1010797Reference(s) to other database(s): GTC:G87424QV, GlycomeDB:
668, CCSD:
47538
Show glycosyltransferases
There is only one chemically distinct structure:
Found 
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