GENETIC ORGANIZATION AND SEQUENCE OF THE RFB GENE-CLUSTER OF YERSINIA-ENTEROCOLITICA SEROTYPE O-3 - SIMILARITIES TO THE DTDP-L-RHAMNOSE BIOSYNTHESIS PATHWAY OF SALMONELLA AND TO THE BACTERIAL POLYSACCHARIDE TRANSPORT-SYSTEMS

The Yersinia enterocolitica O:3 lipopolysaccharide O-antigen is a homo polymer of 6-deoxy-L-altrose. The cloned rfb region was sequenced, and 10 open reading frames were identified. Transposon mutagenesis, delet ion analysis and transcomplementation experiments showed that eight of the genes, organized into two operons, rfbABC and rfbDEFGH, are essen tial for O-antigen synthesis. Functional tandem promoters were identif ied upstream of both operons. Of the deduced polypeptides RfbA, RfbF a nd RfbG were similar to Salmonella proteins involved in the dTDP-L-rha mnose biosynthesis. Rhamnose and 6-deoxy-L-altrose are C3-epimers sugg esting that analogous pathways function in their biosynthesis. RfbD an d RfbE were similar to capsular polysaccharide export proteins, e.g. K psM and KpsT of Escherichia coli. This and transposon mutagenesis show ed that RfbD and RfbE function as O-antigen exporters.