AUTOPHOSPHORYLATION OF A BACTERIAL PROTEIN AT TYROSINE

Autophosphorylation at tyrosine is a common process in eukaryotic kina ses, which is generally modulated by regulatory ligands and affects th e properties of these enzymes. We report that this type of modificatio n occurs also in bacteria, namely in an 81 kDa protein from Acinetobac ter johnsonii. This protein is phosphorylated at the expense of ATP ex clusively at tyrosine residues. It is located in the inner-membrane fr action of cells and can be totally solubilized by detergents. It has b een purified to homogeneity by antiphosphotyrosine immunochromatograph y. Analysis of the peptides released under trypsin proteolysis of the protein has shown that it autophosphorylates at several tyrosine resid ues. The discovery of protein autophosphorylation in bacteria seems of special interest for studying the regulatory aspects of this modifica tion when considering the relative simplicity of the bacterial systems , as compared with most eukaryotic systems, namely in terms of physiol ogy and genetics. (C) 1996 Academic Press Limited