2aaa
From Proteopedia
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CALCIUM BINDING IN ALPHA-AMYLASES: AN X-RAY DIFFRACTION STUDY AT 2.1 ANGSTROMS RESOLUTION OF TWO ENZYMES FROM ASPERGILLUS
Overview
X-ray diffraction analysis (at 2.1-A resolution) of an acid alpha-amylase, from Aspergillus niger allowed a detailed description of the, stereochemistry of the calcium-binding sites. The primary site (which is, essential in maintaining proper folding around the active site) contains a, tightly bound Ca2+ with an unusually high number of eight ligands (O delta, 1 and O delta 2 of Asp175, O delta of Asn121, main-chain carbonyl oxygens, of Glu162 and Glu210, and three water molecules). A secondary binding site, was identified at the bottom of the substrate binding cleft; it involves, the residues presumed to play a catalytic role (Asp206 and Glu230). This, explains the inhibitory effect of calcium observed at higher, concentrations. Neutral Aspergillus oryzae (TAKA) alpha-amylase was also, refined in a new crystal at 2.1-A resolution. The structure of this, homologous (over 80%) enzyme and additional kinetic studies support all, the structural conclusions regarding both calcium-binding sites.
About this Structure
2AAA is a Single protein structure of sequence from Aspergillus niger with CA as ligand. Active as Alpha-amylase, with EC number 3.2.1.1 Full crystallographic information is available from OCA.
Reference
Calcium binding in alpha-amylases: an X-ray diffraction study at 2.1-A resolution of two enzymes from Aspergillus., Boel E, Brady L, Brzozowski AM, Derewenda Z, Dodson GG, Jensen VJ, Petersen SB, Swift H, Thim L, Woldike HF, Biochemistry. 1990 Jul 3;29(26):6244-9. PMID:2207069
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