Isolation of IIIGlc of the phosphoenolpyruvate-dependent glucose phosphotransferase system of Salmonella typhimurium.

We report a procedure for the isolation of IIIglc of Salmonella typhimurium, a protein component of the phosphoenolpyruvate-dependent sugar phosphotransferase system. IIIGlc is a soluble protein with a molecular weight of 21,000, as determined by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified protein is involved in the phosphoenolpyruvate-dependent phosphorylation of methyl alpha-glucoside in vitro. Its affinity for octyl-Sepharose may be an indication of the partial hydrophobic nature of IIIGlc. A specific antiserum against purified IIIGlc was prepared. Growth on different carbon sources did not affect the synthesis of IIIGlc, as determined by quantitative immunoelectrophoresis. Mutations which lower the adenosine 3',5'-phosphate level, such as cya and pts, do not alter the IIIGlc level. The closely related enteric bacteria Escherichia coli and Klebsiella aerogenes contain a protein factor which is closely related to IIIGlc of S. typhimurium, whereas Staphylococcus aureus does not.