PDBsum entry 2aaa

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Glycosidase PDB id
Protein chain
476 a.a.
_CA ×2
Waters ×350

References listed in PDB file
Key reference
Title Calcium binding in alpha-Amylases: an X-Ray diffraction study at 2.1-A resolution of two enzymes from aspergillus.
Authors E.Boel, L.Brady, A.M.Brzozowski, Z.Derewenda, G.G.Dodson, V.J.Jensen, S.B.Petersen, H.Swift, L.Thim, H.F.Woldike.
Ref. Biochemistry, 1990, 29, 6244-6249. [DOI no: 10.1021/bi00478a019]
PubMed id 2207069
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.
Added reference #1*
Title Solution of the structure of Aspergillus niger acid alpha-amylase by combined molecular replacement and multiple isomorphous replacement methods.
Authors R.L.Brady, A.M.Brzozowski, Z.S.Derewenda, E.J.Dodson, G.G.Dodson.
Ref. Acta Crystallogr B, 1991, 47, 527-535.
PubMed id 1930834
*Note, "added" references are those not in the PDB file but which have either been obtained from the journal or suggested by the author(s).
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