CpgA, EF-Tu and the stressosome protein YezB are substrates of the Ser/Thr kinase/phosphatase couple, PrkC/PrpC, in Bacillus subtilis

Abstract

The conservedprpC,prkC,cpgAlocus inBacillus subtilisencodes respectively a Ser/Thr phosphatase, the cognate sensor kinase (containing an external PASTA domain suggested to bind peptidoglycan precursors) and CpgA, a small ribosome-associated GTPase that we have shown previously is implicated in shape determination and peptidoglycan deposition. In this study, in a search for targets of PrkC and PrpC, we showed that,in vitro, CpgA itself is phosphorylated on serine and threonine, and another GTPase, the translation factor EF-Tu, is also phosphorylated by the kinase on the conserved T384 residue. Both substrates are dephosphorylated by PrpCin vitro. In addition, we identified YezB, a 10.3 kDa polypeptide, and a component of the stressosome, as a substrate for both enzymesin vitroand apparentlyin vivo. We propose that the PrpC/PrkC/CpgA system constitutes an important element of a regulatory network involved in the coordination of cell wall expansion and growth inB. subtilis.