UniProt ID: Q5W8I8 |
FUNCTION: Multifunctional transporter that transports L-glutamate as well as multiple ions such as chloride, proton, potassium, sodium and phosphate. At the synaptic vesicle membrane, mainly functions as a uniporter which transports preferentially L-glutamate but also, phosphate from the cytoplasm into synaptic vesicles at presynaptic nerve terminals of excitatory neural cells. The L-glutamate or phosphate uniporter activity is electrogenic and is driven by the proton electrochemical gradient, mainly by the electrical gradient established by the vacuolar H(+)-ATPase across the synaptic vesicle membrane. In addition, functions as a chloride channel that allows a chloride permeation through the synaptic vesicle membrane therefore affects the proton electrochemical gradient and promotes synaptic vesicles acidification. Moreover, functions as a vesicular K(+)/H(+) antiport allowing to maintain the electrical gradient and to decrease chemical gradient and therefore sustain vesicular L-glutamate uptake. The vesicular H(+)/H(+) antiport activity is electroneutral. At the plasma membrane, following exocytosis, functions as a symporter of Na(+) and phosphate from the extracellular space to the cytoplasm allowing synaptic phosphate homeostasis regulation. The symporter activity is driven by an inside negative membrane potential and is electrogenic (By similarity). Also involved in the regulation of retinal hyaloid vessel regression during postnatal development (By similarity). May also play a role in the endocrine L-glutamatergic system of other tissues such as pineal gland and pancreas (By similarity). Required for glutamate release by retinotectal synapses and visual acuity (PubMed:17196531). {ECO:0000250|UniProtKB:Q8BLE7, ECO:0000250|UniProtKB:Q9JI12, ECO:0000269|PubMed:17196531}. CATALYTIC ACTIVITY: Reaction=L-glutamate(out) = L-glutamate(in); Xref=Rhea:RHEA:66336, ChEBI:CHEBI:29985; Evidence={ECO:0000250|UniProtKB:Q9JI12}; CATALYTIC ACTIVITY: Reaction=3 Na(+)(out) + phosphate(out) = 3 Na(+)(in) + phosphate(in); Xref=Rhea:RHEA:71255, ChEBI:CHEBI:29101, ChEBI:CHEBI:43474; Evidence={ECO:0000250|UniProtKB:Q9JI12}; CATALYTIC ACTIVITY: Reaction=phosphate(in) = phosphate(out); Xref=Rhea:RHEA:32823, ChEBI:CHEBI:43474; Evidence={ECO:0000250|UniProtKB:Q9JI12}; CATALYTIC ACTIVITY: Reaction=H(+)(out) + K(+)(in) = H(+)(in) + K(+)(out); Xref=Rhea:RHEA:29467, ChEBI:CHEBI:15378, ChEBI:CHEBI:29103; Evidence={ECO:0000250|UniProtKB:Q9JI12}; CATALYTIC ACTIVITY: Reaction=chloride(in) = chloride(out); Xref=Rhea:RHEA:29823, ChEBI:CHEBI:17996; Evidence={ECO:0000250|UniProtKB:Q9JI12}; ACTIVITY REGULATION: Chloride channel activity is allosterically activated by lumenal H(+) and Cl(-) leading to synaptic vesicles acidification. The L-glutamate transport activity is allosterically activated by lumenal H(+) and Cl(-). The allosteric requirement for H(+) efficiently prevents non-vesicular efflux across the plasma membrane. The L-glutamate uniporter activity exhibits a biphasic dependence on chloride concentration. {ECO:0000250|UniProtKB:Q9JI12}. SUBCELLULAR LOCATION: Cytoplasmic vesicle, secretory vesicle, synaptic vesicle membrane {ECO:0000250}. Membrane {ECO:0000305}; Multi-pass membrane protein {ECO:0000305}. Synapse, synaptosome {ECO:0000250}. Cell membrane {ECO:0000250|UniProtKB:Q8BLE7}; Multi-pass membrane protein {ECO:0000255}. TISSUE SPECIFICITY: Expressed in spinal cord and retinal ganglion cells. {ECO:0000269|PubMed:15515020, ECO:0000269|PubMed:17196531, ECO:0000269|PubMed:17941721}. SIMILARITY: Belongs to the major facilitator superfamily. Sodium/anion cotransporter family. VGLUT subfamily. {ECO:0000305}. |
UniProt ID: Q8JFT2 |
SUBCELLULAR LOCATION: Membrane {ECO:0000256|ARBA:ARBA00004141}; Multi- pass membrane protein {ECO:0000256|ARBA:ARBA00004141}. |
This information was provided by UniProt through a collaboration with ZFIN. (1) |