In Streptomyces hydrogenans, acidic amino acfds 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 ʟ-glutamate and ʟ-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.
Keywords: Acidic Amino Acids; Multiple Transport Systems; Anion and Zwitterion Transport; Streptomyces hydrogenans
Received: 1983-3-4
Published Online: 2014-6-2
Published in Print: 1983-8-1
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