1kwk
From Proteopedia
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| - | | | + | {{STRUCTURE_1kwk| PDB=1kwk | SCENE= }} |
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'''Crystal structure of Thermus thermophilus A4 beta-galactosidase in complex with galactose''' | '''Crystal structure of Thermus thermophilus A4 beta-galactosidase in complex with galactose''' | ||
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[[Category: Shoun, H.]] | [[Category: Shoun, H.]] | ||
[[Category: Wakagi, T.]] | [[Category: Wakagi, T.]] | ||
| - | [[Category: | + | [[Category: Galactose complex]] |
| - | [[Category: | + | [[Category: Glycoside hydrolase family 42]] |
| - | [[Category: | + | [[Category: Tim barrel]] |
| - | [[Category: | + | [[Category: Trimer]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 23:15:27 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 20:15, 2 May 2008
Crystal structure of Thermus thermophilus A4 beta-galactosidase in complex with galactose
Overview
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.
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 Page seeded by OCA on Fri May 2 23:15:27 2008
