Open AccessStructure of Bacillus halmapalus α‐amylase crystallized with and without the substrate analogue acarbose and maltose
Author(s) -
Hobley Timothy J.,
LyhneIversen Louise,
Kaasgaard Svend G.,
Harris Pernille
Publication year - 2006
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
ISSN - 1744-3091
DOI - 10.1107/s174430910603096x
Subject(s) - crystallization , maltose , acarbose , crystallography , chemistry , crystal structure , amylase , substrate (aquarium) , stereochemistry , organic chemistry , enzyme , biology , ecology
Recombinant Bacillus halmapalus α‐amylase (BHA) was studied in two different crystal forms. The first crystal form was obtained by crystallization of BHA at room temperature in the presence of acarbose and maltose; data were collected at cryogenic temperature to a resolution of 1.9 Å. It was found that the crystal belonged to space group P 2 1 2 1 2 1 , with unit‐cell parameters a = 47.0, b = 73.5, c = 151.1 Å. A maltose molecule was observed and found to bind to BHA and previous reports of the binding of a nonasaccharide were confirmed. The second crystal form was obtained by pH‐induced crystallization of BHA in a MES–HEPES–boric acid buffer (MHB buffer) at 303 K; the solubility of BHA in MHB has a retrograde temperature dependency and crystallization of BHA was only possible by raising the temperature to at least 298 K. Data were collected at cryogenic temperature to a resolution of 2.0 Å. The crystal belonged to space group P 2 1 2 1 2 1 , with unit‐cell parameters a = 38.6, b = 59.0, c = 209.8 Å. The structure was solved using molecular replacement. The maltose‐binding site is described and the two structures are compared. No significant changes were seen in the structure upon binding of the substrates.