2amg
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(New page: 200px<br /><applet load="2amg" size="450" color="white" frame="true" align="right" spinBox="true" caption="2amg, resolution 2.0Å" /> '''STRUCTURE OF HYDROLAS...)
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Revision as of 06:06, 21 November 2007
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STRUCTURE OF HYDROLASE (GLYCOSIDASE)
Overview
The three-dimensional structure of an exo-type alpha-amylase from, Pseudomonas stutzeri which degrades starch from its non-reducing end to, produce maltotetraose has been determined by X-ray structure analysis. The, catalytic domain of this enzyme (G4-2), whose structure was determined, is, a product of spontaneous limited proteolysis in culture broth. It has 429, amino acid residues and a molecular mass of 47,200, and crystallizes in, ammonium sulfate solution at pH 7.5. The structure was elucidated by the, multiple isomorphous replacement method and refined at 2.0 A resolution, resulting in a final R-factor of 0.178 for significant reflections with a, root-mean-square deviation from ideality in bond distances of 0.013 A. The, polypeptide chain of this molecule folds into three domains; the first, with a (beta/alpha)8 barrel structure, the second with an excursed part, from the first one, and the third with five-stranded antiparallel, beta-sheets. The active cleft is formed on the C-terminal side of the, beta-sheets in the (beta/alpha)8 barrel as in the known endo-type, alpha-amylases. A histidine side-chain nitrogen ND1 is coordinated to one, of the bound calcium ion. The recognition site of the non-reducing end of, the amylose that determines exo-wise degradation is presumed to be at one, end of this cleft where there is a disordered loop consisting of the 66th, to 72nd residues, and a loop carrying an aspartic acid (Asp160). These, structural features may be responsible for the binding of the non-reducing, end of the substrate amylose.
About this Structure
2AMG is a Single protein structure of sequence from Pseudomonas stutzeri with CA as ligand. This structure superseeds the now removed PDB entry 1AMG. Active as Glucan 1,4-alpha-maltotetraohydrolase, with EC number 3.2.1.60 Full crystallographic information is available from OCA.
Reference
Crystal structure of a maltotetraose-forming exo-amylase from Pseudomonas stutzeri., Morishita Y, Hasegawa K, Matsuura Y, Katsube Y, Kubota M, Sakai S, J Mol Biol. 1997 Apr 4;267(3):661-72. PMID:9126844
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