THE THIRD GENERAL TRANSPORT SYSTEM FOR BRANCHED-CHAIN AMINO ACIDS IN SALMONELLA TYPHIMURIUM

• Published in: Journal of general and applied microbiology Vol. 34; no. 2; pp. 183 - 189
• Main Authors: MATSUBARA, KEIKO, OHNISHI, KUNIHARU, KIRITANI, KAZUYOSHI
• Format: Journal Article
• Language: English
• Published: Tokyo Applied Microbiology, Molecular and Cellular Biosciences Research Foundation 1988; Microbiology Research Foundation
• Subjects: Bacteriology; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Microbiology; Permeability, membrane transport, intracellular transport; Salmonella typhimurium; Characterization; Specificity; Transportation system; Membrane transport; Aminoacid; Bacteria; Affinity; Escherichieae; Salmonella typhimurium; Enterobacteriaceae
• ISSN: 0022-1260; 1349-8037
• DOI: 10.2323/jgam.34.183

Some properties of the LIV-III transport system, a common factor in the entry of branched-chain amino acids in Salmonella typhimurium, have been studied using a double mutant, KA266 (livA brnQ), which is defective in transport via either the LIV-I or LIV-II system. The LIV-III system operates with a low affinity (Km: >15μM) for L-isoleucine, L-leucine, and L-valine. Isoleucine transport via the LIV-III system is inhibited competitively by leucine or valine, but non-competitively by L-cysteine. Uptake of branched-chain amino acids into cells is partially repressed when the bacteria are grown in the presence of 2mM glycyl-L-leucine or more. In the wild type, transport activity of the LIV-III system for isoleucine and leucine is not detected. The LIV-II system appears to show a low affinity for valine similar to the LIV-III system, hence the combined activity of these systems is expressed as the activity of the LIV-III system. The defect in transport via the LIV-II system leads to a great reduction in the transport of valine in the LIV-III system.