title: Conformational ensemble of the sodium-coupled aspartate transporter.
abstract: Sodium and aspartate symporter from Pyrococcus horikoshii, Glt(Ph), is a homolog of the mammalian glutamate transporters, homotrimeric integral membrane proteins that control neurotransmitter levels in brain synapses. These transporters function by alternating between outward-facing and inward-facing states, in which the substrate binding site is oriented toward the extracellular space and the cytoplasm, respectively. Here we used double electron-electron resonance (DEER) spectroscopy to probe the structure and the state distribution of the subunits in the trimer in distinct hydrophobic environments of detergent micelles and lipid bilayers. Our experiments reveal a conformational ensemble of protomers that sample the outward-facing and inward-facing states with nearly equal probabilities, indicative of comparable energies, and independently of each other. On average, the distributions varied only modestly in detergent and in bilayers, but in several mutants unique conformations were stabilized by the latter.
authors: National Biomedical Center for Advanced Electron Spin Resonance Technology, Cornell University, Ithaca, New York, USA.
authors: Elka R
authors: ER
authors: Georgieva
authors: Peter P
authors: PP
authors: Borbat
authors: Christopher
authors: C
authors: Ginter
authors: Jack H
authors: JH
authors: Freed
authors: Olga
authors: O
authors: Boudker
mesh_terms: D026922:Amino Acid Transport Systems, Acidic / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001224:Aspartic Acid / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism; D008823:Micelles; D008958:Models, Molecular; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry; D043902:Pyrococcus horikoshii / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D013057:Spectrum Analysis / Q000379:methods; D013113:Spin Labels
chemical_list: D026922:Amino Acid Transport Systems, Acidic; D019843:Archaeal Proteins; D008051:Lipid Bilayers; D008823:Micelles; D021122:Protein Subunits; D013113:Spin Labels; D001224:Aspartic Acid; D012964:Sodium