title: Effect of alkali ions on the active transport of neutral amino acids into Streptomyces hydrogenans.
abstract: The active transport of neutral amino acids into Streptomyces hydrogenans is inhibited by external Na+. There is no indication that in these cells amino acid accumulation is driven by an inward gradient of Na+. The extent of transport inhibition by Na+ depends on the nature of the amino acid. It decreases with increasing chain length of the amino acid molecules i.e. with increasing non-polar properties of the side chain. Kinetic studies show that Na+ competes with the amino acid for a binding site at the amino acid carrier. There is a close relation between the Ki values for Na+ and the number of C atoms of the amino acids. Other cations also inhibit neutral amino acid uptake competitively; the effectiveness decreases in the order Li+ greater than Na+ greater than K+ greater than Rb+ greater than Cs+. Anions do not have a significant effect on the uptake of neutral amino acids. After prolonged incubation of the cells with 150 mM Na+, in addition to the competitive inhibition of transport Na+ induces an increase in membrane permeability for amino acids.
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000643:Ammonium Chloride / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism; D001665:Binding Sites; D001667:Binding, Competitive; D001693:Biological Transport, Active / Q000187:drug effects; D002414:Cations, Monovalent; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002586:Cesium / Q000494:pharmacology; D002794:Choline / Q000494:pharmacology; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D010539:Permeability; D011188:Potassium / Q000494:pharmacology; D012413:Rubidium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology*; D013302:Streptomyces / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D002414:Cations, Monovalent; D000643:Ammonium Chloride; D002586:Cesium; D008345:Manganese; D008094:Lithium; D012964:Sodium; D008274:Magnesium; D012413:Rubidium; D002794:Choline; D011188:Potassium