Open AccessMonoclinic crystal form of Aspergillus niger α‐amylase in complex with maltose at 1.8 Å resolution
Author(s) -
VujičićŽagar A.,
Dijkstra B. W.
Publication year - 2006
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
ISSN - 1744-3091
DOI - 10.1107/s1744309106024729
Subject(s) - orthorhombic crystal system , maltose , monoclinic crystal system , crystallography , chemistry , molecule , active site , aspergillus niger , stereochemistry , crystallization , crystal structure , aspergillus oryzae , enzyme , organic chemistry , biochemistry
Aspergillus niger α‐amylase catalyses the hydrolysis of α‐1,4‐glucosidic bonds in starch. It shows 100% sequence identity to the A. oryzae homologue (also called TAKA‐amylase), three crystal structures of which have been published to date. Two of them belong to the orthorhombic space group P 2 1 2 1 2 1 with one molecule per asymmetric unit and one belongs to the monoclinic space group P 2 1 with three molecules per asymmetric unit. Here, the purification, crystallization and structure determination of A. niger α‐amylase crystallized in the monoclinic space group P 2 1 with two molecules per asymmetric unit in complex with maltose at 1.8 Å resolution is reported. Furthermore, a novel 1.6 Å resolution orthorhombic crystal form (space group P 2 1 2 1 2) of the native enzyme is presented. Four maltose molecules are observed in the maltose–α‐amylase complex. Three of these occupy active‐site subsites −2 and −1, +1 and +2 and the hitherto unobserved subsites +4 (Asp233, Gly234) and +5 (Asp235). The fourth maltose molecule binds at the distant binding sites d1 (Tyr382) and d2 (Trp385), also previously unobserved. Furthermore, it is shown that the active‐site groove permits different binding modes of sugar units at subsites +1 and +2. This flexibility of the active‐site cleft close to the catalytic centre might be needed for a productive binding of substrate chains and/or release of products.