title: Studies on the transport of anions and zwitterions of acidic amino acids in Streptomyces hydrogenans.
abstract: In Streptomyces hydrogenans, acidic amino acids are taken up either as anions by a specific transport system or as zwitterions via a nonspecific one. Variations in the zwitterion concentration caused by changes in pH influence the uptake and exchange diffusion by the nonspecific system. Differences in pH-optima for L-glutamate and L-aspartate transport are due to the different pK2-values of these amino acids. The anion transport by the specific system is accompanied by a short hyperpolarization of the membrane potential followed by a secondary influx of potassium ions into the cells.
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000600:Amino Acids, Dicarboxylic / Q000378:metabolism*; D001224:Aspartic Acid / Q000378:metabolism; D001692:Biological Transport; D002462:Cell Membrane / Q000502:physiology; D004058:Diffusion; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials; D013302:Streptomyces / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D000596:Amino Acids; D000600:Amino Acids, Dicarboxylic; D005971:Glutamates; D001224:Aspartic Acid; D018698:Glutamic Acid