INVOLVEMENT OF THE GALACTOSYL-1-PHOSPHATE TRANSFERASE ENCODED BY THE SALMONELLA-ENTERICA RFBP GENE IN O-ANTIGEN SUBUNIT PROCESSING

rfbT of Salmonella enterica Ln was previously thought, together with r faL, to be involved in the ligation of polymerized O antigen to core-l ipid A, and three mutants were known. We report the mapping of the mut ations to rfbP, the galactosyl-1-phosphate transferase gene, which is now shown to encode a bifunctional protein. The mutations which have t he former rfbT phenotype are referred to as rfbP(T). We also show that rfbP(T) mutants are not blocked in the ligation step as previously be lieved but in an earlier step, possibly in flipping the O-antigen subu nit on undecaprenyl pyrophosphate from the cytoplasmic to periplasmic face of the cytoplasmic membrane.