The outer membrane permeability mutation of the virulence-associated plasmid ofSalmonella typhimuriumis located in atraT-like gene

Abstract

The SS-A mutation carried by the virulence-as-associated plasmid of Salmonella typhimurium results in increased outer membrane permeability to hydrophobic compounds. A 7.8-kilobase pair BamHI-SalI fragment containing the SS-A mutation was cloned from the virulence-associated plasmid into the cloning vector pACYC184. The cloned DNA segment hybridized with a radioactive probed prepared from the traT gene of R6-5. A similar DNA fragment, cloned from the wild-type virulence-associated plasmid, complemented the SS-A mutant phenotype. Both clones produced a protein that immunologically resembled the R6-5 TraT protein; however, the protein produced by the SS-A containing clone appeared truncated by approximately Mr 1000 indicating an alteration in the primary structure or processing of the protein. We conclude that the mutation producing the SS-A phenotype has occured in a traT-like gene of the Salmonella plasmid.