Regulation of the glucose-specific phosphotransferase system (PTS) of Staphylococcus carnosus by the antiterminator protein GlcT

The ptsG operon of Staphylococcus carnosus consists of two adjacent genes, glcA and glcB, encoding glucose- and glucoside-specific enzymes II, respect ively, the sugar permeases of the phosphoenolpyruvate-dependent phosphotran sferase system (PTS). The expression of the ptsG operon is glucose-inducibl e. Putative RAT (ribonucleic antiterminator) and terminator sequences local ized in the promoter region of glcA suggest regulation via antitermination. The glcT gene was cloned and the putative antiterminator protein GlcT was purified. Activity of this protein was demonstrated in vivo in Escherichia coil and Bacillus subtilis. In vitro studies led to the assumption that pho sphoenolpyruvate-dependent phosphorylation of residue His105 via the genera l PTS components enzyme I and HPr facilitates dimerization of GlcT and cons equently activation. Because of the high similarity of the two ptsG-RAT seq uences of B. subtilis and S. carnosus, in vivo studies were performed in B, subtilis. These indicated that GlcT of S. carnosus is able to recognize pt sG-RAT sequences of B, subtilis and to cause antitermination. The specific interaction between B. subtilis ptsG-RAT and S. carnosus GlcT demonstrated by surface plasmon resonance suggests that only the dimer of GlcT binds to the RAT sequence. HPr-dependent phosphorylation of GlcT facilitates dimer f ormation and may be a control device for the proper function of the general PTS components enzyme I and HPr necessary for glucose uptake and phosphory lation by the corresponding enzyme II.