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1kwk

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{{STRUCTURE_1kwk| PDB=1kwk | SCENE= }}
{{STRUCTURE_1kwk| PDB=1kwk | SCENE= }}
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'''Crystal structure of Thermus thermophilus A4 beta-galactosidase in complex with galactose'''
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===Crystal structure of Thermus thermophilus A4 beta-galactosidase in complex with galactose===
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==Overview==
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The beta-galactosidase from an extreme thermophile, Thermus thermophilus A4 (A4-beta-Gal), is thermostable and belongs to the glycoside hydrolase family 42 (GH-42). As the first known structures of a GH-42 enzyme, we determined the crystal structures of free and galactose-bound A4-beta-Gal at 1.6A and 2.2A resolution, respectively. A4-beta-Gal forms a homotrimeric structure resembling a flowerpot. Each monomer has an active site located inside a large central tunnel. The N-terminal domain of A4-beta-Gal has a TIM barrel fold, as predicted from hydrophobic cluster analysis. The putative catalytic residues of A4-beta-Gal (Glu141 and Glu312) superimpose well with the catalytic residues of Escherichia coli beta-galactosidase. The environment around the catalytic nucleophile (Glu312) is similar to that in the case of E.coli beta-galactosidase, but the recognition mechanism for a substrate is different. Trp182 of the next subunit of the trimer constitutes a part of the active-site pocket, indicating that the trimeric structure is essential for the enzyme activity. Structural comparison with other glycoside hydrolases revealed that many features of the 4/7 superfamily are conserved in the A4-beta-Gal structure. On the basis of the results of 1H NMR spectroscopy, A4-beta-Gal was determined to be a "retaining" enzyme. Interestingly, the active site was similar with those of retaining enzymes, but the overall fold of the TIM barrel domain was very similar to that of an inverting enzyme, beta-amylase.
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{{ABSTRACT_PUBMED_12215416}}
==About this Structure==
==About this Structure==
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[[Category: Tim barrel]]
[[Category: Tim barrel]]
[[Category: Trimer]]
[[Category: Trimer]]
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Revision as of 08:10, 2 July 2008

Image:1kwk.png

Template:STRUCTURE 1kwk

Crystal structure of Thermus thermophilus A4 beta-galactosidase in complex with galactose

Template:ABSTRACT PUBMED 12215416

About this Structure

1KWK is a Single protein structure of sequence from Thermus thermophilus. Full crystallographic information is available from OCA.

Reference

Trimeric crystal structure of the glycoside hydrolase family 42 beta-galactosidase from Thermus thermophilus A4 and the structure of its complex with galactose., Hidaka M, Fushinobu S, Ohtsu N, Motoshima H, Matsuzawa H, Shoun H, Wakagi T, J Mol Biol. 2002 Sep 6;322(1):79-91. PMID:12215416

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