2xwi | pdb_00002xwi

SiaP R147K mutant in complex with Neu5Ac

spinqualitylabelsall models 2xwi, resolution 2.19Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2xwi is a 1 chain structure with sequence from Haemophilus influenzae. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.195Å Ligands: SLB Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function SIAP_HAEIN Part of the tripartite ATP-independent periplasmic (TRAP) transport system SiaPT involved in the uptake of sialic acid. This protein specifically binds sialic acid with high affinity. Publication Abstract from PubMed Tripartite ATP-independent periplasmic (TRAP) transporters are secondary transporters that have evolved an obligate dependence on a substrate binding protein (SBP) to confer unidirectional transport. Different members of the DctP-family of TRAP SBPs have binding sites that recognise a diverse range of organic acid ligands, but appear to only share a common electrostatic interaction between a conserved arginine and a carboxylate group in the ligand. We investigated the significance of this interaction using the sialic acid-specific SBP, SiaP, from the Haemophilus influenzae virulence-related SiaPQM TRAP transporter. Using in vitro, in vivo and structural methods applied to SiaP, we demonstrate that the coordination of the acidic ligand moiety of sialic acid by the conserved arginine (R147) is essential for the function of the transporter as a high-affinity scavenging system. However, at higher substrate concentration the transporter can function in the absence of R147 suggesting that this bi-molecular interaction in not involved in further stages of the transport cycle. As well as being required for high affinity binding, we also demonstrate that the R147 is a strong selectivity filter for carboxylate-containing substrates in TRAP transporters, by engineering the SBP to recognise a non-carboxylate containing substrate, sialylamide, through water-mediated interactions. Together these data provide biochemical and structural support for the hypothesis that TRAP transporters function predominantly as high-affinity transporters for carboxylate-containing substrates. Tripartite ATP-independent periplasmic (TRAP) transporters use an arginine-mediated selectivity filter for high affinity substrate binding.,Fischer M, Hopkins AP, Severi E, Hawkhead J, Bawdon D, Watts AG, Hubbard RE, Thomas GH J Biol Chem. 2015 Sep 5. pii: jbc.M115.656603. PMID:26342690 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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