title: The entry process as the target for energy input in active transport of alpha-aminoisobutyric acid by Mycobacterium phlei.
abstract: Mycobacterium phlei was shown to accumulate alpha-aminoisobutyric acid, establishing a concentration gradient of approximately 15,000-fold. The apparent affinity constant of the carrier for alpha-aminoisobutyric acid was 1.8 microM. The system exhibited a broad specificity provided two structural requirements were satisfied: the presence of a free amino and carboxyl group on the alpha carbon and the absence of a net charge. The role of energy coupling on the accumulation of alpha-aminoisobutyric acid was studied by two different kinds of experiments, the relative effects of the inhibitors on the rate of entry and the steady-state of accumulation, and a comparison of the efflux induced at the final steady state by the addition of (a) excess nonradioactive alpha-aminoisobutyric acid, (b) energy inhibitors, or (c) both. The results are consistent with the hypothesis that accumulation of alpha-aminoisobutyric acid is due to an increased rate of entry, the rate of exit not being affected by metabolic inhibitors.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000621:Aminoisobutyric Acids / Q000378:metabolism*; D001426:Bacterial Proteins / Q000032:analysis; D001693:Biological Transport, Active / Q000187:drug effects; D002462:Cell Membrane / Q000032:analysis; D004734:Energy Metabolism; D009161:Mycobacterium / Q000378:metabolism*; D009168:Mycobacterium phlei / Q000378:metabolism*; D014867:Water / Q000032:analysis
chemical_list: D000596:Amino Acids; D000621:Aminoisobutyric Acids; D001426:Bacterial Proteins; D014867:Water