The oxyR gene from Erwinia carotovora: cloning, sequence analysis and expression in Escherichia coli

Homologs of the Escherichia coli oxyR gene were identified in several Erwinia species, using a combination of PCR and Southern hybridization analysis. The oxyR gene from Erwinia carotovora was isolated on a cosmid clone and characterized. The gene and deduced gene product shared high level sequence identity with their E. coli counterparts (78 and 89% identity, respectively). In E. coli, the oxyR gene is a transcriptional activator that, under oxidizing conditions, induces expression of a set of oxidative defence genes. OxyR null mutants are, therefore, sensitive to hydrogen peroxide. Introduction of the E. carotovora oxyR gene into an E. coli oxyR mutant resulted in transformants that were hydrogen peroxide resistant, indicating that the Erwinia protein was functional in E. coli.