1kwk

<table><tr><td colspan='2'>[[1kwk]] is a 1 chain structure with sequence from [http://en.wikipedia.org/wiki/"flavobacterium_thermophilum"_yoshida_and_oshima_1971 "flavobacterium thermophilum" yoshida and oshima 1971]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1KWK OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1KWK FirstGlance]. <br>

</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=ACT:ACETATE+ION'>ACT</scene>, <scene name='pdbligand=CL:CHLORIDE+ION'>CL</scene>, <scene name='pdbligand=GAL:BETA-D-GALACTOSE'>GAL</scene>, <scene name='pdbligand=MPD:(4S)-2-METHYL-2,4-PENTANEDIOL'>MPD</scene>, <scene name='pdbligand=ZN:ZINC+ION'>ZN</scene></td></tr>

<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Beta-galactosidase Beta-galactosidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.23 3.2.1.23] </span></td></tr>

<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1kwk FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1kwk OCA], [http://pdbe.org/1kwk PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=1kwk RCSB], [http://www.ebi.ac.uk/pdbsum/1kwk PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=1kwk ProSAT]</span></td></tr>

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== Publication Abstract from PubMed ==

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.

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<ref>PMID:12215416</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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<div class="pdbe-citations 1kwk" style="background-color:#fffaf0;"></div>

== References ==

<references/>

[[Category: Flavobacterium thermophilum yoshida and oshima 1971]]

[[Category: Beta-galactosidase]]

[[Category: Fushinobu, S]]

[[Category: Hidaka, M]]

[[Category: Matsuzawa, H]]

[[Category: Motoshima, H]]

[[Category: Ohtsu, N]]

[[Category: Shoun, H]]

[[Category: Wakagi, T]]

[[Category: Trimer]]