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Analysis of the Serratia marcescens proBA operon and feedback control of proline biosynthesis
1Research Laboratory of Applied Biochemistry, Tanabe Seiyaku Co. Ltd, Osaka, Japan.
Abstract:
The proBA operon, coding for gamma-glutamyl kinase (GK) and gamma-glutamyl phosphate reductase (GPR), was cloned from the chromosome of the wild-type strain of Serratia marcescens Sr41. From our sequence data the proB (1101 bp) and proA (1472 bp) genes were shown to code for two proteins of Mr 39,169 and 44,640, respectively. Analysis of expression of the lacZ structural gene fused with the proBA promoter showed that the proBA operon is not subject to proline-mediated feedback repression. Amplification of the proBA operon enabled us to determine GK activity, which was inhibited in the presence of a low concentration of L-proline. Comparison of the amino acid sequences of the S. marcescens GK and GPR proteins with those of the GK and GPR proteins from E. coli revealed extensive similarities.