1glm
From Proteopedia
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REFINED CRYSTAL STRUCTURES OF GLUCOAMYLASE FROM ASPERGILLUS AWAMORI VAR. X100
Overview
The refined crystal structures of a proteolytic fragment of glucoamylase, from Aspergillus awamori var. X100 have been determined at pH 6 and 4 to a, resolution of 2.2 A and 2.4 A, respectively. The models include the, equivalent of residues 1 to 471 of glucoamylase from Aspergillus niger and, a complete interpretation of the solvent structure. The R-factors of the, pH 6 and 4 structures are 0.14 and 0.12, respectively, with, root-mean-square deviations of 0.014 A and 0.012 A from expected, bondlengths. The enzyme has the general shape of a doughnut. The "hole" of, the doughnut consists of a barrier of hydrophobic residues at the center, which separates two water-filled voids, one of which serves as the active, site. Three clusters of water molecules extend laterally from the active, site. One of the lateral clusters connects the deepest recess of the, active site to the surface of the enzyme. The most significant difference, in the pH 4 and 6 structures is the thermal parameter of water 500, the, putative nucleophile in the hydrolysis of maltooligosaccharides. Water 500, is associated more tightly with the enzyme at pH 4 (the pH of optimum, catalysis) than at pH 6. In contrast to water 500, Glu179, the putative, catalytic acid of glucoamylase, retains the same conformation in both, structures and is in an environment that would favor the ionized, rather, than the acid form of the side-chain. Glycosyl chains of 5 and 8 sugar, residues are linked to Asparagines 171 and 395, respectively. The, conformations of the two glycosyl chains are similar, being superimposable, on each other with a root-mean-square discrepancy of 1.9 A. The N-glycosyl, chains hydrogen bond to the surface of the protein through their terminal, sugars, but otherwise do not interact strongly with the enzyme. The, structures have ten serine/threonine residues, to each of which is linked, a single mannose sugar. The structure of the ten O-glycosylated residues, taken together suggests a well-defined conformation for proteins that have, extensive O-glycosylation of their polypeptide chain.
About this Structure
1GLM is a Single protein structure of sequence from Aspergillus awamori with MAN as ligand. Active as Glucan 1,4-alpha-glucosidase, with EC number 3.2.1.3 Full crystallographic information is available from OCA.
Reference
Refined crystal structures of glucoamylase from Aspergillus awamori var. X100., Aleshin AE, Hoffman C, Firsov LM, Honzatko RB, J Mol Biol. 1994 May 13;238(4):575-91. PMID:8176747
Page seeded by OCA on Tue Nov 20 16:09:19 2007
