1y3p
From Proteopedia
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Structure of AlgQ1, alginate-binding protein, complexed with an alginate tetrasaccharide
Overview
A Gram-negative bacterium, Sphingomonas sp. A1, has a macromolecule, (alginate) import system consisting of a pit on the cell surface and an, alginate-specific ATP-binding cassette importer in the inner membrane., Transport of alginate from the pit to the ABC importer is probably, mediated by two periplasmic binding protein homologues (AlgQ1 and AlgQ2)., Here we describe characteristics of binding of AlgQ1 and AlgQ2 to alginate, and its oligosaccharides through surface plasmon resonance biosensor, analysis, UV absorption difference spectroscopy, and X-ray, crystallography. Both AlgQ1 and AlgQ2 were inducibly expressed in the, periplasm of alginate-grown cells of strain A1. Biosensor analysis, indicated that both proteins specifically bind alginate with a high degree, of polymerization (>100) and that dissociation constants for alginate with, an average molecular mass of 26 kDa are 2.3 x 10(-)(7) M for AlgQ1 and 1.5, x 10(-)(7) M for AlgQ2. An in vitro ATPase assay using the membrane, complex, including the alginate ABC importer, suggested that both, alginate-bound forms of AlgQ1 and AlgQ2 are closely associated with the, importer. X-ray crystallography showed that AlgQ1 consisted of two domains, separated by a deep cleft that binds alginate oligosaccharides through a, conformational change in the two domains. These results directly show that, alginate-binding proteins play an important role in the efficient, transport of alginate macromolecules with different degrees of, polymerization in the periplasm.
About this Structure
1Y3P is a Single protein structure of sequence from Sphingomonas sp. with CA as ligand. Full crystallographic information is available from OCA.
Reference
Direct evidence for Sphingomonas sp. A1 periplasmic proteins as macromolecule-binding proteins associated with the ABC transporter: molecular insights into alginate transport in the periplasm., Momma K, Mishima Y, Hashimoto W, Mikami B, Murata K, Biochemistry. 2005 Apr 5;44(13):5053-64. PMID:15794643
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