Autoregulation of PurR repressor synthesis and involvement of purR in the regulation of pur B, purC, purL, purMN and guaBA expression in Escherichia coli


Correspondence to M. Kilstrup, Institute of Biological Chemistry B, University of Copenhagen, Sølvgade 83, DK-1307, Copenhagen K, Denmark


The pur R gene encodes a repressor (PurR) controlling the synthesis of the enzymes of purine biosynthesis. The subunit of PurR was identified as a 38-kDa polypeptide by SDS/polyacrylamide gel electrophoresis. Analysis of a pur R–lacZ transcriptional fusion indicated that pur R expression is autoregulated. This was confirmed by gel retardation and DNasel footprinting experiments, where two PurR-binding sites were identified in the transcribed part of pur R. Introduction of a purR mutation in wild-type and pur – lac fusion strains was found to abolish purine repression of all genes of the purine biosynthetic pathway except for pur A.