Sequences and evolutionary analyses of eukaryotic-type protein kinases from Streptomyces coelicolor A3(2)

Four eukaryotic-type protein serine/threonine kinases from Streptomyces coe licolor A3(2) were cloned and sequenced. To explore evolutionary relationsh ips between these and other protein kinases, the distribution of protein se rine/threonine kinase genes in prokaryotes was examined with the TFASTA pro gram. Genes of this type were detected in only a few species of prokaryotes and their distribution was uneven: Streptomyces, Mycobacterium, Synechocys tis and Myxococcus each contained more than three such genes. Homology anal yses by GAP and Rdf2 programs suggested that some kinases from one species were closely related, whilst others were only remotely related. This was co nfirmed by examining phylogenetic trees constructed by the neighbour-joinin g and other methods. For each species, analysis of the coding regions indic ated that the G+C content of protein kinase genes was similar to that of ot her genes. Considered with the fact that in phylogenetic trees the amino ac id sequences of STPK from Aquifex aeolicus and some other eukaryotic-type p rotein kinases in prokaryotes form a cluster with protein kinases from euka ryotes, this suggests that the eukaryotic-type protein kinases were present originally in both prokaryotes and eukaryotes, but that most of these gene s have been lost during the evolutionary process in prokaryotes because the y are not needed. This conclusion is supported by the observation that the prokaryotes retaining several of these kinases undergo complicated morpholo gical and/or biochemical differentiation.