Bacteriorhodopsin drives the glutamate transporter of synaptic vesicles after co-reconstitution.
Active accumulation of neurotransmitters by synaptic vesicles is an essential component of the synaptic transmission cycle. Isolated vesicles show energy-dependent uptake of several transmitters by processes which are apparently mediated by a proton electrochemical potential across the vesicle membrane. Although this energy gradient is probably generated by a proton ATPase, the functional separation of ATP cleavage and transmitter uptake activity has only been shown clearly for monoamine transport. We report here that the light-driven proton pump, bacteriorhodopsin, can replace the endogenous proton ATPase in proteoliposomes reconstituted from vesicular detergent extracts. The system shows light-dependent uptake of glutamate with properties very similar to those observed in intact vesicles, e.g. chloride dependence or stimulation by NH4+. Our experiments show that the proton pump and the glutamate transporter are separate entities and provide a powerful tool for further characterization of the glutamate carrier.
Maycox
P R
PR
Department of Neurochemistry, Max-Planck-Institute for Psychiatry, Martinsried, FRG.
Deckwerth
T
T
Jahn
R
R
D027322:Amino Acid Transport System X-AG; D000818:Animals; D001436:Bacteriorhodopsins / Q000494:pharmacology*; D001693:Biological Transport, Active / Q000187:drug effects; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D006023:Glycoproteins / Q000378:metabolism*; D066298:In Vitro Techniques; D008081:Liposomes; D051381:Rats; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism*; D014316:Tritium
D027322:Amino Acid Transport System X-AG; D005971:Glutamates; D006023:Glycoproteins; D008081:Liposomes; D014316:Tritium; D018698:Glutamic Acid; D001436:Bacteriorhodopsins