Comparative proteome analysis of Streptomyces mobaraensis under MgCl2 stress shows proteins modulating differentiation and transglutaminase biosynthesis

Abstract

Much effort has been devoted to studying the production of Streptomyces transglutaminase (TGase). However, more exploration into the mechanism of TGase biosynthesis is necessary to enhance its production further. The effect of excessive metal stress on Streptomyces mobaraensis's TGase activity, growth rate, and mycelium differentiation were evaluated. To elucidate the regulatory mechanism of TGase production and cell differentiations, a proteomic analysis and qRT-PCR of S. mobaraensis was performed. This study showed that the TGase biosynthesis was enhanced while the cell growth was inhibited under MgCl2 stress at the earlier stage of incubation. Furthermore, MgCl2 stress resulted in early cell differentiation compared to the control group. The proteomic analysis indicated that both the nucleotide metabolism and primary metabolism were repressed at the onset of TGase production, explaining the observed decrease in cell growth rate. Several enriched enzymes in the nitrogen metabolic pathways confirmed that the metabolic fluxes for the syntheses of glycine and serine were increased. Furthermore, some stress or stress-related proteins were expressed at a low level in the strain cultivated in normal medium but were highly expressed at the onset of TGase production.