Microbial Protein Tyrosine Kinases [Signal Transduction]

February 19th, 2014 by Chao, J. D., Wong, D., Av-Gay, Y.

Microbial ester kinases identified in the past three decades came as a surprise, as protein phosphorylation on Ser, Thr and Tyr amino acids was thought to be unique to eukaryotes. Current analysis of available microbial genomes reveals that eukaryotic-like protein kinases are prevalent in prokaryotes and can converge in the same signaling pathway with the classical microbial "two component" systems. Most microbial tyrosine kinases lack the "eukaryotic" Hanks domain signature and are designated tyrosine kinases based upon their biochemical activity. These include the tyrosine kinases termed bacterial tyrosine kinases, or BY-kinases, which are responsible for the majority of known bacterial tyrosine phosphorylation events. Although termed generally as bacterial tyrosine kinases, BY-kinases can be considered as one family belonging to the superfamily of prokaryotic protein tyrosine kinases (PPTKs) in bacteria. Other members of this superfamily include atypical "odd" tyrosine kinases with diverse mechanisms of protein phosphorylation, and the "eukaryotic-like" Hanks type tyrosine kinases. Here we discuss the distribution, phylogeny and function of the various PPTKs focusing on the recently discovered Mycobacterium tuberculosis PtkA and its relationship with other members of this diverse family of proteins.