The identification of distinct protein kinases and phosphatases in the prokaryote Salmonella typhimurium.

The finding of protein phosphorylation in prokaryotes (Wang, J. Y. J., and Koshland, D. E. (1978) J. Biol. Chem. 253, 7605-7608) has been pursued further. The prokaryotic organism Salmonella typhimurium is shown to contain at least 10 phosphorylated proteins with serine or threonine phosphates which are produced by the action of at lest four protein kinases. The protein kinases are distinguished by their substrate specificity, their chromatographic behavior, and their inhibition patterns. The phosphorylations are reversible, and more than one protein phosphatase activity exists in these cells. The presence of specific protein kinases and phosphatases suggests that this form of protein covalent modification is involved in the regulation of different cellular functions in prokaryotes as it is in eukaryotes.