2v25: Difference between revisions

The PEB1a protein is an antigenic factor exposed on the surface of the, food-borne human pathogen Campylobacter jejuni, which has a major role in, adherence and host colonisation. PEB1a is also the periplasmic binding, protein component of an aspartate/glutamate ABC transporter essential for, optimal microaerobic growth on these dicarboxylic amino acids. Here, we, report the crystal structure of PEB1a at 1.5 A resolution. The protein has, a typical two-domain alpha/beta structure, characteristic of periplasmic, extracytoplasmic solute receptors and a chain topology related to the type, II subfamily. An aspartate ligand, clearly defined by electron density in, the interdomain cleft, forms extensive polar interactions with the, protein, the majority of which are made with the larger domain. Arg89 and, Asp174 form ion-pairing interactions with the main chain alpha-carboxyl, and alpha-amino-groups, respectively, of the ligand, while Arg67, Thr82, Lys19 and Tyr156 co-ordinate the ligand side-chain carboxyl group. Lys19, and Arg67 line a positively charged groove, which favours binding of Asp, over the neutral Asn. The ligand-binding cleft is of sufficient depth to, accommodate a glutamate. This is the first structure of an ABC-type, aspartate-binding protein, and explains the high affinity of the protein, for aspartate and glutamate, and its much weaker binding of asparagine and, glutamine. Stopped-flow fluorescence spectroscopy indicates a simple, bimolecular mechanism of ligand binding, with high association rate, constants. Sequence alignments and phylogenetic analyses revealed PEB1a, homologues in some Gram-positive bacteria. The alignments suggest a more, distant homology with GltI from Escherichia coli, a known glutamate and, aspartate-binding protein, but Lys19 and Tyr156 are not conserved in GltI., Our results provide a structural basis for understanding both the solute, transport and adhesin/virulence functions of PEB1a.

2V25 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Campylobacter_jejuni Campylobacter jejuni] with ZN and ASP as [http://en.wikipedia.org/wiki/ligands ligands]. Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2V25 OCA].  

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