Analysis of Low Temperature Inducible Mechanism of γ-Glutamyltranspeptidase of Escherichia coli K-12

Abstract

Escherichia coli K-12 cultured at 20°C has more γ-glutamyltranspeptidase (GGT: EC 2.3.2.2) activity than that cultured at 37 or 42°C. On Western blot analysis, E. coli K-12 cells cultured at 20°C produced more GGT protein than those cultured at 37°C. mRNA of the GGT gene (ggt) in the cells was also measured and it was found that the level of ggt mRNA at 20°C was 10-fold higher than that at 37°C. When the ggt promoter was replaced by a tac promoter, GGT activity at 37°C from the tac promoter was 5-fold higher than that at 37°C from the ggt promoter, though there was less difference in GGT activity between both grown at 20°C. The ggt mRNA at 20°C was found to be more stable than that at 37°C. These results suggested that the higher GGT activity in E. coli K-12 cells grown at 20°C was due to a higher level of GGT protein at 20°C caused by higher level of ggt mRNA at 20°C because of a low-temperature dependent ggt promoter as well as the stability of ggt mRNA at 20°C.

Key words:

• Escherichia coli
• gene expression
• γ-glutamyltranspeptidase
• promoter analysis