Characterization of Eukaryotic-like Protein Kinase (Stk)-mediated Protein Phosphorylation in Escherichia coli

摘要

Extensive Tyr-specific kinase acitivity of Stk were characterized by LC-MSMS combined with selective phosphopeptide enrichments. Differential protein expressions by Stk kinase in E. coli were characterized by label-free quantitation based on spectral counting. Stk showed no significant sequence motifs for substrate binding, yet 40percent of Stk substrates > 80percent of phsophorylation events share common motifs with mammalian kinases. Eukaryotic-like kinase Stk, expressed by phage gene in prophage form, is possibily involved in host bacterial cell activities as seen in up- and down-regulated protein expressions in a broad range. Lower kinase activity of Stk was detected in EDL933 strain compared to that in K12strain, which suggests unknown control mechanisms involved in Stk activation.