The prokaryotic origin and evolution of eukaryotic chemosignaling systems.

Analysis of our own results and data published over the last two decades supports the authors' hypothesis of the prokaryotic origin and endosymbiotic mechanism of appearance of chemosignaling systems in higher eukaryotes. Comparison of the structural-functional organization of these information systems and their component blocks (receptors, GTP-binding proteins, enzymes with cyclase activity, protein kinases, etc.) in bacteria and eukaryotes revealed a whole series of similar characteristics pointing to evolutionary relatedness. This led to the conclusion that eukaryotic signal systems have prokaryotic roots. In terms of their architecture and functional properties, the signal transduction systems seen in unicellular eukaryotes represent a transitional stage in the evolution of chemosignaling systems between prokaryotes and higher eukaryotes. The propagation of chemosignaling systems in three kingdoms - Bacteria, Archaea, and Eukarya - occurred by horizontal transfer of bacterial genes and the coevolution of the components of these systems.