Abstract
A structural gene responsible for the high-affinity transport system of branched-chain amino acids, livA, is located at 76-77min, near xyl, on the genetic map of Salmonella typhimurium. Although the regulatory gene, livR, has been located in the same region as the livA, linkage relationship between the livA and livR genes is not yet known. The livA mutation does not affect the activity of leucine-isoleucine-valine-threonine binding protein. Isoleucine-valine requiring mutants can take up enough amounts of these amino acids for growth through only the low-affinity transport system(s), even if the high-affinity system is defective.
