Effects of heterologous expression of CspB, the major cold shock protein of Bacillus subtilis, on protein synthesis in Escherichia coli

The major cold shock protein of Bacillus subtilis, CspB, has been shown to affect the level of several cold-induced proteins in B. subtilis after cold shock. Here we show that the expression of CspB in Escherichia coli at 37° C – conditions where the cold shock proteins CspA and CspB of E. coli are not present – resulted in a marked decrease in cellular growth rate and had a profound influence on the pattern of protein synthesis, as revealed by two-dimensional gel electrophoresis. This involves both decreases and increases in the rates of synthesis of specific proteins. Specifically, CspB induction resulted in enhanced β-galactosidase activity expressed from a transcriptional hns-lacZ fusion. This increase reflects the induction of hns transcription and H-NS synthesis after cold shock, which has been demonstrated to be dependent on CspA in vitro. In contrast, expression of a mutant form of CspB (CspBF15A) that is unable to bind to ssDNA in vitro had no effect on growth rate, pattern of protein synthesis or β-galactosidase activity. Our data demonstrate a strong influence of CspB on protein synthesis in E. coli and suggest a similar function for CspA in E. coli to that of CspB in B. subtilis.