Membrane topology of the Salmonella enterica serovar Typhimurium Group B O-antigen translocase Wzx.
The O-antigen translocase, Wzx, is involved in translocation of bacterial polysaccharide repeat units across the cytoplasmic membrane, and is an unusually diverse, highly hydrophobic protein, with high numbers of predicted alpha-helical transmembrane segments (TMS). The Salmonella enterica serovar Typhimurium Group B O-antigen Wzx was an ideal candidate for topological study as the O-antigen gene cluster is one of only a few that have been well characterized. The topology profile prediction for this protein was determined using five programs, with different recognition parameters, which consistently predict that 12 TMS are present. A membrane topology model was constructed by analysis of lacZ and phoA gene fusions at randomly selected and targeted fusion sites within wzx. Enzyme activity of these, and full-length C-terminal fusion proteins, confirmed the 12-TMS topology for this Wzx, and also indicated that the C-terminus was located within the cytoplasm, which is consistent with the predicted topology.
Cunneen
Monica M
MM
School of Molecular and Microbial Biosciences, University of Sydney, Sydney, NSW, Australia.
Reeves
Peter R
PR
D000469:Alkaline Phosphatase / Q000235:genetics; D000595:Amino Acid Sequence; D007763:Lac Operon / Q000235:genetics; D026901:Membrane Transport Proteins / Q000737:chemistry*; D008958:Models, Molecular; D019081:O Antigens; D011993:Recombinant Fusion Proteins / Q000235:genetics; D012486:Salmonella typhimurium / Q000737:chemistry* / Q000201:enzymology* / Q000235:genetics
D026901:Membrane Transport Proteins; D019081:O Antigens; D011993:Recombinant Fusion Proteins; D000469:Alkaline Phosphatase