title: Protein phosphorylation in Escherichia coli and purification of a protein kinase.
abstract: More than 40 protein species including RNA polymerase were found to be phosphorylated in Escherichia coli on analyses of 32P-labeled cell lysates by single and two-dimensional gel electrophoresis and autoradiography. The protein species and the level of phosphorylation varied depending on the cell growth phase. With [gamma-32P]ATP as a substrate, cell lysates phosphorylated endogenous proteins in vitro which were predominantly phosphorylated in vivo. Both serine and threonine were the major phosphate acceptors in whole cell lysates. Starting from a partially purified RNA polymerase preparation with the protein phosphorylation activity and using an E. coli protein with an apparent Mr = 90K (K represents X 1000) as the substrate, we purified a protein kinase with a native Mr approximately 120K to apparent homogeneity. The protein kinase is either a heterodimer of 61K and 66K polypeptides or a homodimer of one of these polypeptides. We also isolated a 100K protein with self-phosphorylation activity.
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism*; D008970:Molecular Weight; D010766:Phosphorylation; D011494:Protein Kinases / Q000302:isolation & purification*
chemical_list: D001426:Bacterial Proteins; D011494:Protein Kinases