A IIIman protein is involved in the transport of glucose,mannose and fructose by oral streptococci

We show in this article that the transport of glucose, mannose and fructose by the phosphoenolpyruvate: mannose phosphotransferase system of oral streptococci requires the participation of a protein component that we have called III_man. This protein was purified from Streptococcus salivarius by chromatography on DEAE-cellulose, DEAE-TSK, hydroxyapatite, and Dyematrex Green A. The purified protein migrated as a 38,900 molecular weight protein on a sodium dodecyl sulfate polyacrylamide gel. However, electrophoretic analysis of phosphoproteins and Western blot experiments indicated the presence in membrane-free cellular extracts of S. salivarius of 2 different forms of III_man having molecular weights of 38,900 and 35,200. The presence of the high-molecular-weight form of III_man was observed by immunodiffusion. Western blot and phosphorylation by [³²]PEP in S. salivarius, Streptococcus mutans, Streptococcus sobrinus, and Streptococcus lactis but not in Streptococcus faecium, Staphylococcus aureus, Bacillus subtilis and Lactobacillus casei. Antibodies directed against the III_man of S. salivarius did not react with the III_man of Escherichia coli.