C-terminal half of Salmonella enterica WbaP (RfbP) is the galactosyl-1-phosphate transferase domain catalyzing the first step of O-antigen synthesis

The C-terminal end of the Salmonella enterica wbaP gene controls the initial galactosyltransferase (GT) step of O-antigen synthesis as wbaP with an intact C-terminal and a mutant N-terminal retains GT activity. The C-terminal controls the transfer of galactosyl-1-phosphate from GDP-galactose to undecaprenyl phosphate. The N-terminal controls the later stage (T) of the synthesis which involves the release of undecaprenyl pyrophosphate-Gal from WbaP. The T stage occurs before the O-antigen flips from the cytoplasmic end to the periplasmic end of the cytoplasmic membrane.