8ctc
Human excitatory amino acid transporter 3 (EAAT3) with bound glutamate in an intermediate outward facing state
Structural highlights
DiseaseEAA3_HUMAN Hot water reflex epilepsy;Dicarboxylic aminoaciduria. The disease is caused by variants affecting the gene represented in this entry. Disease susceptibility is associated with variants affecting the gene represented in this entry. A deletion at the chromosome 9p24.2 locus, including SLC1A1, has been identified in patients with psychotic disorders (PubMed:21982423). This 84 kb deletion is immediately upstream of the SLC1A1 gene in a regulatory region that contains the full native promoter sequence, extends through exon 1 of the SLC1A1 mRNA, co-segregates with disease in an extended 5-generation pedigree and increases disease risk more than 18-fold for family members (PubMed:23341099).[1] [2] FunctionEAA3_HUMAN Sodium-dependent, high-affinity amino acid transporter that mediates the uptake of L-glutamate and also L-aspartate and D-aspartate (PubMed:21123949, PubMed:26690923, PubMed:33658209, PubMed:7521911, PubMed:7914198, PubMed:8857541). Can also transport L-cysteine (PubMed:21123949). Functions as a symporter that transports one amino acid molecule together with two or three Na(+) ions and one proton, in parallel with the counter-transport of one K(+) ion (PubMed:26690923, PubMed:33658209, PubMed:7521911, PubMed:8857541). 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:26690923, PubMed:8857541). Plays an important role in L-glutamate and L-aspartate reabsorption in renal tubuli (PubMed:21123949). Plays a redundant role in the rapid removal of released glutamate from the synaptic cleft, which is essential for terminating the postsynaptic action of glutamate (By similarity). Contributes to glutathione biosynthesis and protection against oxidative stress via its role in L-glutamate and L-cysteine transport (By similarity). Negatively regulated by ARL6IP5 (By similarity).[UniProtKB:P51906][UniProtKB:P51907][3] [4] [5] [6] [7] [8] Publication Abstract from PubMedExcitatory amino acid transporters (EAATs) uptake glutamate into glial cells and neurons. EAATs achieve million-fold transmitter gradients by symporting it with three sodium ions and a proton, and countertransporting a potassium ion via an elevator mechanism. Despite the availability of structures, the symport and antiport mechanisms still need to be clarified. We report high-resolution cryo-EM structures of human EAAT3 bound to the neurotransmitter glutamate with symported ions, potassium ions, sodium ions alone, or without ligands. We show that an evolutionarily conserved occluded translocation intermediate has a dramatically higher affinity for the neurotransmitter and the countertransported potassium ion than outward- or inward-facing transporters and plays a crucial role in ion coupling. We propose a comprehensive ion coupling mechanism involving a choreographed interplay between bound solutes, conformations of conserved amino acid motifs, and movements of the gating hairpin and the substrate-binding domain. Symport and antiport mechanisms of human glutamate transporters.,Qiu B, Boudker O Nat Commun. 2023 May 4;14(1):2579. doi: 10.1038/s41467-023-38120-5. PMID:37142617[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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