5nv9
Substrate-bound outward-open state of a Na+-coupled sialic acid symporter reveals a novel Na+-siteSubstrate-bound outward-open state of a Na+-coupled sialic acid symporter reveals a novel Na+-site
Structural highlights
FunctionSIAT_PROMH Symporter that uses the Na(+) gradient as the driving force for the uptake of the sialic acid N-acetylneuraminic acid (Neu5Ac) (PubMed:29717135). It allows the use of host-derived Neu5Ac as an energy source by P.mirabilis (PubMed:29717135). Also binds N-glycolylneuraminic acid (Neu5Gc) and ketodeoxynonulosonic acid (KDN) (PubMed:29717135). Shows the highest affinity for Neu5Ac and Neu5Gc, which commonly occupy the terminal non-reducing position of mammalian cell surface glycoconjugates (PubMed:29717135).[1] Publication Abstract from PubMedMany pathogenic bacteria utilise sialic acids as an energy source or use them as an external coating to evade immune detection. As such, bacteria that colonise sialylated environments deploy specific transporters to mediate import of scavenged sialic acids. Here, we report a substrate-bound 1.95 A resolution structure and subsequent characterisation of SiaT, a sialic acid transporter from Proteus mirabilis. SiaT is a secondary active transporter of the sodium solute symporter (SSS) family, which use Na(+) gradients to drive the uptake of extracellular substrates. SiaT adopts the LeuT-fold and is in an outward-open conformation in complex with the sialic acid N-acetylneuraminic acid and two Na(+) ions. One Na(+) binds to the conserved Na2 site, while the second Na(+) binds to a new position, termed Na3, which is conserved in many SSS family members. Functional and molecular dynamics studies validate the substrate-binding site and demonstrate that both Na(+) sites regulate N-acetylneuraminic acid transport. Substrate-bound outward-open structure of a Na(+)-coupled sialic acid symporter reveals a new Na(+) site.,Wahlgren WY, Dunevall E, North RA, Paz A, Scalise M, Bisignano P, Bengtsson-Palme J, Goyal P, Claesson E, Caing-Carlsson R, Andersson R, Beis K, Nilsson UJ, Farewell A, Pochini L, Indiveri C, Grabe M, Dobson RCJ, Abramson J, Ramaswamy S, Friemann R Nat Commun. 2018 May 1;9(1):1753. doi: 10.1038/s41467-018-04045-7. PMID:29717135[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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