Cloning of the regulatory locus ompB of Salmonella typhimurium LT-2. I. Isolation of the ompR gene and identification of its gene product.

We have cloned the complete functional ompB locus of Salmonella typhimurium LT-2 into Escherichia coli K-12 using a cosmid vector and in vitro packaging into lambda. The ompB locus of Salmonella was found to complement both envZ and ompR mutations in E. coli as well as an ompR mutation of Salmonella. The ompR part of the ompB locus was further subcloned into the multicopy plasmid pKN410 as a 1.3 kb fragment. This fragment coded for a single 28.5 kd protein corresponding to about 820 bp in length. Furthermore, the OmpR proteins of S. typhimurium and E. coli were shown to be structurally and functionally highly similar.