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Membrane topology of the Drosophila vesicular glutamate transporter
Author(s) -
Fei Hao,
Karnezis Tara,
Reimer Richard J.,
Krantz David E.
Publication year - 2007
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2007.04518.x
Subject(s) - membrane topology , transmembrane protein , cytosol , drosophila melanogaster , biology , microbiology and biotechnology , transmembrane domain , cytoplasm , synaptic vesicle , amino acid , biochemistry , glutamate receptor , topology (electrical circuits) , biophysics , vesicle , membrane , gene , enzyme , receptor , mathematics , combinatorics
The vesicular glutamate transporters (VGLUTs) are responsible for packaging glutamate into synaptic vesicles, and are part of a family of structurally related proteins that mediate organic anion transport. Standard computer‐based predictions of transmembrane domains have led to divergent topological models, indicating the need for experimentally derived predictions. Here we present data on the topology of the VGLUT ortholog from Drosophila melanogaster (DVGLUT). Using immunofluorescence assays of DVGLUT transiently localized to the plasma membrane of heterologously transfected cells, we have determined the accessibility of epitope tags inserted into the lumenal/extracellular face of the protein. Using immunoisolation, we have identified complementary tagged sites that face the cytoplasm. Our data show that DVGLUT contains 10 hydrophobic regions that completely span the membrane (TMs 1–10) and that the amino and carboxyl termini are cytosolic. Importantly, between TMs 4 and 5 is an unforeseen cytosolic loop of some 50 residues. Other domains exposed to the cytosol include loops between TMs 6–7 and 8–9, and regions C‐terminal to TM2 and N‐terminal to TM3. Between TM2 and 3 is a potentially hydrophobic, but topologically ambiguous region. Lumenal domains include sequences between TMs 1–2, 3–4, 5–6, 7–8 and 9–10. These data provide a basis for determining structure‐function relationships for DVGLUT and other related proteins.