COMPONENTS OF HISTIDINE TRANSPORT: HISTIDINE-BINDING PROTEINS AND hisP PROTEIN

TLDR: The high-affinity transport system for histidine in Salmonella typhimurium has been resolved into three components: J, K, and P, which is a histidine-binding protein released by osmotic shock; hisJ mutants lack the binding protein and are defective in histidine transport; hisP mutants, though defective in transport, have normal levels of J binding protein.

Abstract: The high-affinity (Km = 3 × 10-8 M) transport system for histidine in Salmonella typhimurium has been resolved into three components: J, K, and P. J, which is a histidine-binding protein released by osmotic shock, is specified by the hisJ gene: hisJ mutants lack the binding protein and are defective in histidine transport. Another class of mutants—dhuA, which is closely linked to hisJ—has five times the normal level of binding protein and has an increased rate of histidine transport. P, which is a protein specified by the hisP gene, is required for J binding protein to be operative in transport. hisP mutants, though defective in transport, have normal levels of J binding protein. K, a third transport component, works in parallel to J, and also requires the P protein in order to be operative in transport. A second histidine-binding protein has been found but its relation to K is unclear. hisJ, dhuA, and hisP have been mapped and are in a cluster (near purF) on the S. typhimurium chromosome.