Serine-Threonine Protein Kinases of Cyanobacteria.

Protein phosphorylation is a pivotal mechanism for signal transduction, regulation of biochemical processes essential for reproduction, growth, and adaptation of organisms to changing conditions. Bacteria, which emerged more than 3.5 billion years ago, faced the need to adapt to a variety of ecological niches from the very beginning of their existence. It is not surprising that they developed a wide range of different types of kinases and target amino acid residues for phosphorylation. To date, many examples of phosphorylation of serine, threonine, tyrosine, histidine, arginine, lysine, aspartate, and cysteine have been discovered. Bacterial histidine kinases as part of two-component systems have been studied in most detail. More recently eukaryotic type serine-threonine and tyrosine kinases based on the conserved catalytic domain have been described in the genomes of many bacteria. The term "eukaryotic" is misleading, since evolutionary origin of these enzymes goes back to the last common universal ancestor - LUCA. Bioinformatics, molecular genetics, omics, and biochemical strategies combined provide new tools for researchers to establish relationship between the kinase abundance/activity and proteome changes, including studying of the kinase signaling network (kinome) within the cell. This manuscript presents several approaches to investigation of the serine-threonine protein kinases of cyanobacteria, as well as their combination, which allow to suggest new hypotheses and strategies for researchers.