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A unique type of GABA binding by Mycobacterium leprae
K Prabhakaran1, E B Harris, B Randhawa
1Laboratory Research Branch, Hansen's Disease Center, U.S. Public Health Service, Carville, Louisiana 70721.
Microbios
|January 1, 1992
Summary
Mycobacterium leprae binds gamma-aminobutyric acid (GABA) with high affinity. These bacterial GABA receptors are non-neuronal, differing from those in other organisms.
Area of Science:
- Microbiology
- Neuroscience
- Biochemistry
Background:
- Mycobacterium leprae exhibits neurotropism, an unusual characteristic among bacteria.
- The bacterium produces glutamic acid decarboxylase, which synthesizes gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter.
Purpose of the Study:
- To investigate the in vitro binding of GABA by Mycobacterium leprae.
- To characterize the nature and properties of GABA binding sites on M. leprae.
Main Methods:
- Utilized 3H-GABA as a substrate to study GABA binding kinetics.
- Assessed the specificity and affinity of GABA binding sites.
- Investigated the effect of known neuronal GABA receptor modulators.
Main Results:
- Mycobacterium leprae possesses high-affinity binding sites for GABA.
- GABA uptake by M. leprae is a specific, saturable process with a Km of 66.7 pM.
- Optimal binding occurred at pH 7.3 and 37°C, and was rapid (complete within 5 min).
- Neuronal GABA receptor antagonists and agonists did not significantly affect M. leprae GABA binding.
Conclusions:
- The GABA receptors on M. leprae are of a non-neuronal type.
- These bacterial receptors differ from those found in neurons, spermatozoa, and Pseudomonas.
- This finding provides insight into the unique neurotropic mechanisms of M. leprae.