2r5o
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(New page: 200px<br /><applet load="2r5o" size="350" color="white" frame="true" align="right" spinBox="true" caption="2r5o, resolution 1.300Å" /> '''Crystal structure o...)
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Revision as of 09:28, 23 January 2008
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Crystal structure of the C-terminal domain of wzt
Overview
ATP-binding-cassette (ABC) transporters are responsible for the export of, a wide variety of cell-surface glycoconjugates in both Gram-positive and, Gram-negative bacteria. These include the O-antigenic polysaccharide, (O-PS) portion of lipopolysaccharide, a crucial virulence determinant in, Gram-negative pathogens. O-PSs are synthesized by one of two fundamentally, different pathways. Escherichia coli O serotypes O8 and O9a provide the, prototype systems for studying O-PS export via ABC transporters. The, transporter is composed of the transmembrane component Wzm and the, nucleotide-binding component Wzt. Although the N-terminal domain of Wzt is, a conventional ABC protein, the C-terminal domain of Wzt (C-Wzt) is a, unique structural element that determines the specificity of the, transporter for either the O8 or O9a O-PS. We show here that the two, domains of Wzt can function when expressed as separate polypeptides; both, are essential for export. In vitro, C-Wzt binds its cognate O-PS by, recognizing a residue located at the nonreducing end of the polymer. The, crystal structure of C-Wzt(O9a) is reported here and reveals a beta, sandwich with an immunoglobulin-like topology that contains the, O-PS-binding pocket. Substrate interactions with nucleotide-binding, domains have been demonstrated in an ABC exporter previously. However, to, our knowledge substrate binding by a discrete, cytoplasmic accessory, domain in an extended nucleotide-binding domain polypeptide has not, previously been demonstrated. Elucidation of the substrate-recognition, system involved in O-PS export provides insight into the mechanism that, coordinates polymer biosynthesis, termination, and export.
About this Structure
2R5O is a Single protein structure of sequence from Escherichia coli with , and as ligands. Full crystallographic information is available from OCA.
Reference
Substrate binding by a bacterial ABC transporter involved in polysaccharide export., Cuthbertson L, Kimber MS, Whitfield C, Proc Natl Acad Sci U S A. 2007 Dec 4;104(49):19529-34. Epub 2007 Nov 21. PMID:18032609
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