1KWK

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

1KWK の概要

• エントリーDOI: 10.2210/pdb1kwk/pdb
• 関連するPDBエントリー: 1KWG
• 分子名称: BETA-GALACTOSIDASE, beta-D-galactopyranose, CHLORIDE ION, ... (7 entities in total)
• 機能のキーワード: tim barrel, glycoside hydrolase family 42, trimer, galactose complex, hydrolase
• 由来する生物種: Thermus thermophilus
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 73544.38

構造登録者

Hidaka, M.,Fushinobu, S.,Ohtsu, N.,Motoshima, H.,Matsuzawa, H.,Shoun, H.,Wakagi, T. (登録日: 2002-01-29, 公開日: 2002-10-02, 最終更新日: 2024-03-13)

主引用文献

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

PubMed Abstract: 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.

PubMed: 12215416
DOI: 10.1016/S0022-2836(02)00746-5

実験手法

X-RAY DIFFRACTION (2.2 Å)