1ia5
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(New page: 200px<br /><applet load="1ia5" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ia5, resolution 2.00Å" /> '''POLYGALACTURONASE FR...)
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Revision as of 15:05, 20 November 2007
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POLYGALACTURONASE FROM ASPERGILLUS ACULEATUS
Overview
Polygalacturonases hydrolyze the alpha-(1-4) glycosidic bonds of, de-esterified pectate in the smooth region of the plant cell wall. Crystal, structures of polygalacturonase from Aspergillus aculeatus were determined, at pH 4.5 and 8.5 both to 2.0 A resolution. A. aculeatus polygalacturonase, is a glycoprotein with one N and ten O-glycosylation sites and folds into, a right-handed parallel beta-helix. The structures of the three, independent molecules are essentially the same, showing no dependency on, pH or crystal packing, and are very similar to that of Aspergillus niger, polygalacturonase. However, the structures of the long T1 loop containing, a catalytic tyrosine residue are significantly different in the two, proteins. A three-dimensional model showing the substrate binding mode for, a family 28 hydrolase was obtained by a combined approach of flexible, docking, molecular dynamics simulations, and energy minimization. The, octagalacturonate substrate was modeled as an unbent irregular helix with, the -1 ring in a half-chair ((4)H(3)) form that approaches the transition, state conformation. A comparative modeling of the three polygalacturonases, with known structure shows that six subsites ranging from -4 to +2 are, clearly defined but subsites -5 and +3 may or may not be shaped depending, on the nearby amino acid residues. Both distal subsites are mostly exposed, to the solvent region and have weak binding affinity even if they exist., The complex model provides a clear explanation for the functions, either, in catalysis or in substrate binding, of all conserved amino acid residues, in the polygalacturonase family of proteins. Modeling suggests that the, role of the conserved Asn157 and Tyr270, which had previously been, unidentified, may be in transition state stabilization. In A. niger, polygalacturonase, the long T1 loop may have to undergo conformational, change upon binding of the substrate to bring the tyrosine residue close, to subsite -1.
About this Structure
1IA5 is a Single protein structure of sequence from Aspergillus aculeatus with MAN as ligand. Active as Polygalacturonase, with EC number 3.2.1.15 Full crystallographic information is available from OCA.
Reference
The X-ray structure of Aspergillus aculeatus polygalacturonase and a modeled structure of the polygalacturonase-octagalacturonate complex., Cho SW, Lee S, Shin W, J Mol Biol. 2001 Aug 24;311(4):863-78. PMID:11518536
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