gamma-Aminobutyric acid uptake by a bacterial system with neurotransmitter binding characteristics.
gamma-Aminobutyric acid (GABA), an amino acid, has been found in every class of living organisms. In higher organisms, GABA is a neurotransmitter and binds with high affinity and specificity to GABA receptors on neurons in a sodium-independent reaction that is saturable. The role of GABA in organisms lacking nervous tissue is not known. This report describes, in a strain of Pseudomonas fluorescens, a GABA uptake system with binding characteristics like those of the GABA (type A) brain receptor. The binding was saturable and specific for GABA, was sodium-independent, was of high affinity (Km = 65 nM), and was inhibited competitively by muscimol, a potent GABA analogue. The bacterial GABA system included a homogeneous binding site, and no cooperative interaction was found between sites. To our knowledge, such a system for GABA, or other neurotransmitters, in a bacterium has not been reported.
Guthrie
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Department of Biochemistry, School of Medicine, Indiana University, Evansville 47712.
Nicholson-Guthrie
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CS
D001667:Binding, Competitive; D007700:Kinetics; D009118:Muscimol / Q000494:pharmacology; D011551:Pseudomonas fluorescens / Q000378:metabolism*; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology
D011963:Receptors, GABA-A; D009118:Muscimol; D005680:gamma-Aminobutyric Acid