Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The carnitine transporter was solubilized from rat renal apical plasma membrane (brush-border membrane) with C12E8 and reconstituted into liposomes by removing the detergent from mixed micelles by hydrophobic chromatography on Amberlite XAD-4. The reconstitution was optimised with respect to the protein concentration, the detergent/phospholipid ratio and the number of passages through a single Amberlite column. The reconstituted carnitine transporter catalysed a first-order antiport reaction (carnitine/carnitine or carnitine/substrate) stimulated by external, not internal, Na+, with a positive cooperativity. Na+ was co-transported with carnitine. Optimal activity was found between pH 5.5 and pH 6.0. The sulfhydryl reagents MTSES, MTSET and mercurials strongly inhibited the transport. Substrate analogues inhibited the transport; the most effective were acylcarnitines and betaine, followed by dimethylglicine, tetraethylammonium and arginine. Besides carnitine, only acylcarnitines and betaine were efficiently translocated. The Km for carnitine on the external and internal side of the transporter was 0.08 and 1.2 mM, respectively. The transporter is asymmetrical and it is unidirectionally inserted into the proteoliposomal membrane with an orientation corresponding to that of the native membrane. The reconstituted carnitine transporter corresponds, very probably, to the OCTN2 protein.
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PMID:Reconstitution into liposomes and functional characterization of the carnitine transporter from renal cell plasma membrane. 1496 77

The present study aimed to elucidate the distribution of betaine/gamma-aminobutyric acid (GABA) transporter-1 (BGT-1) in the normal monkey cerebral neocortex and hippocampus by immunoperoxidase and Immunogold labelling. BGT-1 was observed in pyramidal neurons in the cerebral neocortex and the CA fields of the hippocampus. Large numbers of small diameter dendrites or dendritic spines were observed in the neuropil. These made asymmetrical synaptic contacts with unlabelled axon terminals containing small round vesicles, characteristic of glutamatergic terminals. BGT-1 label was observed in an extra-perisynaptic region, away from the post-synaptic density. Immunoreactivity was not observed in portions of dendrites that formed symmetrical synapses, axon terminals, or glial cells. The distribution of BGT-1 on dendritic spines, rather than at GABAergic axon terminals, suggests that the transporter is unlikely to play a major role in terminating the action of GABA at a synapse. Instead, the osmolyte betaine is more likely to be the physiological substrate of BGT-1 in the brain, and the presence of the transporter in pyramidal neurons suggests that these neurons utilize betaine to maintain osmolarity.
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PMID:A light and electron microscopic study of betaine/GABA transporter distribution in the monkey cerebral neocortex and hippocampus. 1532 81