2AAA

CALCIUM BINDING IN ALPHA-AMYLASES: AN X-RAY DIFFRACTION STUDY AT 2.1 ANGSTROMS RESOLUTION OF TWO ENZYMES FROM ASPERGILLUS

Summary for 2AAA

• Entry DOI: 10.2210/pdb2aaa/pdb
• Descriptor: ALPHA-AMYLASE, CALCIUM ION (3 entities in total)
• Functional Keywords: glycosidase
• Biological source: Aspergillus niger
• Total number of polymer chains: 1
• Total formula weight: 53045.22

Authors

Brady, L.,Brzozowski, A.M.,Derewenda, Z.,Dodson, E.J.,Dodson, G.G. (deposition date: 1991-02-27, release date: 1993-07-15, Last modification date: 2024-06-05)

Primary citation

Boel, E.,Brady, L.,Brzozowski, A.M.,Derewenda, Z.,Dodson, G.G.,Jensen, V.J.,Petersen, S.B.,Swift, H.,Thim, L.,Woldike, H.F.
Calcium binding in alpha-amylases: an X-ray diffraction study at 2.1-A resolution of two enzymes from Aspergillus.
Biochemistry, 29:6244-6249, 1990

PubMed Abstract: 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.

PubMed: 2207069
DOI: 10.1021/bi00478a019

Experimental method

X-RAY DIFFRACTION (2.12 Å)