A single amino acid substitution in a mannosyltransferase, WbdA, converts the Escherichia coli O9 polysaccharide into O9a: generation of a new O-serotype group.

ABSTRACT: wbdA is a mannosyltransferase gene that is involved in synthesis of the Escherichia coli O9a polysaccharide, a mannose homopolymer with a repeating unit of 2-alphaMan-1,2-alphaMan-1,3-alphaMan-1, 3-alphaMan-1. The equivalent structural O polysaccharide in the E. coli O9 and Klebsiella O3 strains is 2-alphaMan-1,2-alphaMan-1, 2-alphaMan-1,3-alphaMan-1,3-alphaMan-1, with an excess of one mannose in the 1,2 linkage. We have cloned wbdA genes from these O9 and O3 strains and shown by genetic and functional studies that wbdA is the only gene determining the O-polysaccharide structure of O9 or O9a. Based on functional analysis of chimeric genes and site-directed mutagenesis, we showed that a single amino acid substitution, C55R, in WbdA of E. coli O9 converts the O9 polysaccharide into O9a. DNA

SUBMITTER: Kido N 

PROVIDER: S-EPMC111322 | biostudies-literature | 2000 May

REPOSITORIES: biostudies-literature