Diversity and specificity of protein-phosphorylating systems in bacteria.

Bacteria harbor three different protein-phosphorylating systems which regulate distinct physiological processes: first, the nucleotide-dependent system which modifies hydroxyl groups of amino acids in protein substrates; second, the two-component system which involves both sensor kinase and response regulator; third, the phosphoenolpyruvate-dependent phosphotransferase system. These systems share a number of structural and functional similarities with the protein-phosphorylating systems of eukaryotes.