OVERPRODUCTION, ISOLATION, AND DNA-BINDING CHARACTERISTICS OF XRE, THE REPRESSOR PROTEIN FROM THE BACILLUS-SUBTILIS DEFECTIVE PROPHAGE PBSX

PBSX is a phage-like bacteriocin (phibacin) of Bacillus subtilis 168. Lysogeny is maintained by the PBSX-encoded repressor, Xre. The Xre pro tein was overproduced in Escherichia coli and isolated by affinity chr omatography. Gel retardation and DNase I footprinting studies indicate d that Xre binds to four sites close to its own gene. These sites over lap putative promoters for xre and a divergent transcriptional unit, c ontaining the middle genes.