4izm
From Proteopedia
Crystal structure of GltPh L66C-S300C mutant crosslinked with divalent mercury
Structural highlights
FunctionGLT_PYRHO Sodium-dependent, high-affinity amino acid transporter that mediates aspartate uptake (PubMed:17435767, PubMed:19380583, PubMed:17230192, Ref.11). Has only very low glutamate transport activity (PubMed:19380583, PubMed:17230192). Functions as a symporter that transports one amino acid molecule together with two or three Na(+) ions, resulting in electrogenic transport (PubMed:17435767, PubMed:19380583, Ref.11). Na(+) binding enhances the affinity for aspartate (PubMed:19380583, Ref.11). Mediates Cl(-) flux that is not coupled to amino acid transport; this avoids the accumulation of negative charges due to aspartate and Na(+) symport (PubMed:17435767). In contrast to mammalian homologs, transport does not depend on pH or K(+) ions (PubMed:19380583).[1] [2] [3] [PDB:4P19] Publication Abstract from PubMedGlutamate transporters catalyze concentrative uptake of the neurotransmitter into glial cells and neurons. Their transport cycle involves binding and release of the substrate on the extra- and intracellular sides of the plasma membranes and translocation of the substrate-binding site across the lipid bilayers. The energy of the ionic gradients, mainly sodium, fuels the cycle. Here, we used a cross-linking approach to trap a glutamate transporter homolog from Pyrococcus horikoshii in key conformational states with the substrate-binding site facing either the extracellular or the intracellular side of the membrane to study binding thermodynamics. We show that the chemical potential of sodium ions in solution is exclusively coupled to substrate binding and release, not to substrate translocation. Despite the transporter's structural symmetry, the binding mechanisms are distinct on the opposite sides of the membrane and more complex than the current models suggest. Binding thermodynamics of a glutamate transporter homolog.,Reyes N, Oh S, Boudker O Nat Struct Mol Biol. 2013 May;20(5):634-40. doi: 10.1038/nsmb.2548. Epub 2013 Apr, 7. PMID:23563139[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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