3bcd: Difference between revisions

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{{STRUCTURE_3bcd|  PDB=3bcd  |  SCENE=  }}  
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'''Alpha-amylase B in complex with maltotetraose and alpha-cyclodextrin'''
===Alpha-amylase B in complex with maltotetraose and alpha-cyclodextrin===




==Overview==
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The gene for a membrane-bound, halophilic, and thermostable alpha-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 A away from the active site. The structure of AmyB with the inhibitor acarbose at 1.35 A resolution shows that a nonasaccharide has been synthesized through successive transglycosylation reactions of acarbose. Unexpectedly, in a complex of wild-type AmyB with alpha-cyclodextrin and maltoheptaose at 2.2 A 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 (2)S(o) 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.
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==About this Structure==
==About this Structure==
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[[Category: Raw starch binding]]
[[Category: Raw starch binding]]
[[Category: Thermostable]]
[[Category: Thermostable]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Apr 24 09:48:13 2008''
 
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 04:56:18 2008''

Revision as of 01:56, 29 July 2008

File:3bcd.png

Template:STRUCTURE 3bcd

Alpha-amylase B in complex with maltotetraose and alpha-cyclodextrin

Template:ABSTRACT PUBMED 18387632

About this Structure

3BCD is a Single protein structure of sequence from Halothermothrix orenii. Full crystallographic information is available from OCA.

Reference

Crystal structure of the polyextremophilic alpha-amylase AmyB from Halothermothrix orenii: details of a productive enzyme-substrate complex and an N domain with a role in binding raw starch., Tan TC, Mijts BN, Swaminathan K, Patel BK, Divne C, J Mol Biol. 2008 May 9;378(4):850-68. Epub 2008 Feb 29. PMID:18387632

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