1992 Volume 112 Issue 4 Pages 541-546
The three-dimensional structure of a complex of soybean β-amylase [EC 3. 2. 1. 2] with an inhibitor, α-cyclodextrin, has been determined at 3.0 Å resolution by X-ray diffraction analysis. Preliminary chain tracing showed that the enzyme folded into large and small domains. The large domain has a (βα)8 super-secondary structure, while the smaller one is formed from two long loops extending from the β3 and β4 strands of the (βα)8 structure. The interface of the two domains together with shorter loops from the (βα)8 structure form a deep cleft, in which α-cyclodextrin binds slightly away from the center. Two maltose molecules also bind in the cleft. One shares a binding site with α-cyclodextrin and the other is situated more deeply in the cleft.
