2amg: Difference between revisions

[[Image:2amg.gif|left|200px]]<br /><applet load="2amg" size="350" color="white" frame="true" align="right" spinBox="true"  

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.

2AMG is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Pseudomonas_stutzeri Pseudomonas stutzeri] with <scene name='pdbligand=CA:'>CA</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. This structure supersedes the now removed PDB entry 1AMG. Active as [http://en.wikipedia.org/wiki/Glucan_1,4-alpha-maltotetraohydrolase Glucan 1,4-alpha-maltotetraohydrolase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.60 3.2.1.60] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2AMG OCA].  

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