Overview of protein phosphorylation in bacteria with a main focus on unusual protein kinases in Bacillus subtilis

Protein phosphorylation is a post-translational modification that affects protein activity through the addition of a phosphate moiety by protein kinases or phosphotransferases. It occurs in all life forms. In addition to Hanks kinases found also in eukaryotes, bacteria encode membrane histidine kinases that, with their cognate response regulator, constitute two-component systems and phosphotransferases that phosphorylate proteins involved in sugar utilization on histidine and cysteine residues. In addition, they encode BY-kinases and arginine kinases that phosphorylate protein specifically on tyrosine and arginine residues respectively. They also possess unusual bacterial protein kinases illustrated here by examples from Bacillus subtilis.