Amino Acid Transport in Bacteria

Publisher Summary This chapter describes the mechanism of transport along with the genetic and regulatory interrelationships of multiple transport systems for an amino acid. The chapter focuses on LIV-I, which is a high-affinity branched chain amino acid transport system in Escherichia coli ( E.coli ). Some of the physiological and regulatory relationships of amino acid transporters are also presented, including a newly recognized global regulator, the leucine-responsive regulatory protein (Lrp). The LIV-binding protein (LIV-BP) bounds leucine, isoluecine, and valine, and it is a component of the LIV-I transport system. The leucine-specific binding protein (LS-BP) binds D- and L-leucine as a component of the LS system. The high-affinity branched chain amino acid transport system is regulated by both repression and transcription attenuation. Transcription attenuation control of LIV-I expression is identified genetically. High-affinity transport activity is altered by mutations in several genes involved in the formation of mature, charged leucyl-tRNA Leu . The cloning and sequence analysis of the LIV-I regulon provide a molecular framework that can account for the previous genetic results.