Analysis of the Serratia marcescens proBA operon and feedback control of proline biosynthesis

Abstract

The proBA operon, coding for γ-glutamyl kinase (GK) and γ-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 M r 39169 and 44640, 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.