Please use this identifier to cite or link to this item:
|Title:||Crystal Structure of the Polyextremophilic α-Amylase AmyB from Halothermothrix orenii: Details of a Productive Enzyme-Substrate Complex and an N Domain with a Role in Binding Raw Starch|
|Citation:||Tan, T.-C., Mijts, B.N., Swaminathan, K., Patel, B.K.C., Divne, C. (2008-05-09). Crystal Structure of the Polyextremophilic α-Amylase AmyB from Halothermothrix orenii: Details of a Productive Enzyme-Substrate Complex and an N Domain with a Role in Binding Raw Starch. Journal of Molecular Biology 378 (4) : 850-868. ScholarBank@NUS Repository. https://doi.org/10.1016/j.jmb.2008.02.041|
|Abstract:||The gene for a membrane-bound, halophilic, and thermostable α-amylase, AmyB, from Halothermothrix orenii was cloned and sequenced. The crystal structure shows that, in addition to the typical domain organization of family 13 glycoside hydrolases, AmyB carries an additional N-terminal domain (N domain) that forms a large groove-the N-C groove-some 30 Å away from the active site. The structure of AmyB with the inhibitor acarbose at 1.35 Å resolution shows that a nonasaccharide has been synthesized through successive transglycosylation reactions of acarbose. Unexpectedly, in a complex of wild-type AmyB with α-cyclodextrin and maltoheptaose at 2.2 Å resolution, a maltotetraose molecule is bound in subsites - 1 to + 3, spanning the cleavage point at - 1/+ 1, with the - 1 glucosyl residue present as a 2So skew boat. This wild-type AmyB complex was obtained in the presence of a large excess of substrate, a condition under which it is possible to capture Michaelis complexes, which may explain the observed binding across - 1/+ 1 and ring distortion. We observe three methionine side chains that serve as "binding platforms" for glucosyl rings in AmyB, a seemingly rare occurrence in carbohydrate-binding proteins. The structures and results from the biochemical characterization of AmyB and AmyB lacking the N domain show that the N domain increases binding of the enzyme to raw starch. Furthermore, theoretical modeling suggests that the N-C groove can accommodate, spatially and chemically, large substrates such as A-starch. © 2008 Elsevier Ltd. All rights reserved.|
|Source Title:||Journal of Molecular Biology|
|Appears in Collections:||Staff Publications|
Show full item record
Files in This Item:
There are no files associated with this item.
checked on Jan 16, 2019
WEB OF SCIENCETM
checked on Jan 16, 2019
checked on Jan 11, 2019
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.