Investigating the role of the C-terminal domain in McsB, a structurally unique tyrosine kinase found in Bacillus subtilis

James Graham, The College of Wooster

Abstract

McsB is a recently described prokaryotic protein tyrosine kinase found in Bacillus subtilis. In addition to autophosphorylation activity, McsB can be further induced to phosphorylate other targets upon binding a second protein, McsA, encoded in the same operon as McsB. McsB is a structurally unique tyrosine kinase in that its N-terminus corresponds to a guanidine-phosphotransferase domain and is critical for kinase activity. However, the adjacent C-terminal domain is not homologous to other protein domains and its role in McsB protein kinase activity is unknown. We created a series of deletion mutants to determine what portions of the C-terminal domain were important for kinase activity and/or its regulation by McsA. Additionally, two point mutations were made in a region identified by the deletion mutations as critical for enzymatic function. Our hypothesis was that the C-terminal domain regulated activity by either blocking access to the active site by acting as a pseudo substrate, or by holding the enzyme in a conformationally inactive state until bound by McsA. The deletion mutations identified a region which appears to be critical for enzymatic function while two arginine residues located within this region were shown be important but not essential for activity of the enzyme.