Identification of a sulfhydryl-reducing agent-inducible protein highly homologous to protein synthesis elongation factor Tu in Bacillus subtilis

It was examined that the effect of beta-mercaptoethanol and dithiothreitol treatments, which should affect disulfide bond formation of proteins, on cellular protein components of Bacillus subtilis. In LB medium, the treatments induced the synthesis of a 50 kD protein (P50), which is synthesized constitutively under normal growth condition and is a major cytoplasmic protein. P50 was also induced by heat shock, but not by sporulation. In Schaeffer's sporulation medium, however, P50 was not induced by the sulfhydryl-reducing agents. This suggests that the sulfhydryl-reducing agent-inducibility of P50 might depent on specific physiological condition(s). The amino terminal sequences of two of the four main V8 protease fragments of P50 were determined. A search in databases revealed that P50 was highly homologous to protein synthesis elongation factor Tu of B. subtilis.