Histidine and aromatic permeases of Salmonella typhimurim.

Mutants defective either in the histidine permease (hisP) or in the aromatic permease (aroP) were isolated in Salmonella typhimurium and were characterized. The hisP locus had a 49% linkage to purF by phage transduction. The aroP locus was close to proA. Merozygotes diploid for the hisP gene were constructed by episomal transfer, and hisP(+) was dominant over hisP. The properties of merozygotes are described and discussed. A method for the selection of revertants of hisP mutants was devised. By this method, one of the hisP mutants was characterized as an amber mutant. The specificity of the aromatic permease was investigated by using as substrates analogues of the aromatic amino acids and of histidine.