3VT0

Crystal structure of Ct1,3Gal43A in complex with lactose

3VT0 の概要

• エントリーDOI: 10.2210/pdb3vt0/pdb
• 関連するPDBエントリー: 3VT1 3VT2 3vsf 3vsz
• 関連するBIRD辞書のPRD_ID: PRD_900004
• 分子名称: Ricin B lectin, beta-D-galactopyranose-(1-4)-beta-D-glucopyranose, GLYCEROL (3 entities in total)
• 機能のキーワード: gh43, cbm13, galactan hydrolysis, sugar binding protein
• 由来する生物種: Clostridium thermocellum
• タンパク質・核酸の鎖数: 6
• 化学式量合計: 354049.94

構造登録者

Jiang, D.,Fan, J.,Wang, X.,Zhao, Y.,Huang, B.,Zhang, X.C. (登録日: 2012-05-18, 公開日: 2012-12-05, 最終更新日: 2024-03-20)

主引用文献

Jiang, D.,Fan, J.,Wang, X.,Zhao, Y.,Huang, B.,Liu, J.,Zhang, X.C.
Crystal structure of 1,3Gal43A, an exo-beta-1,3-galactanase from Clostridium thermocellum
J.Struct.Biol., 180:447-457, 2012

PubMed Abstract: Glycoside hydrolase family 43 (GH43) consists of a variety of enzymes distributed widely in prokaryotes and eukaryotes. The mechanism by which GH43 enzymes hydrolyze oligosaccharides requires three essential acidic amino acid residues. However, one of them is thought to be missing in galactan β-1,3-galactosidases from the GH43 family. Ct1,3Gal43A, from Clostridium thermocellum, is comprised of a GH43 domain, a CBM13 domain, and a dockerin domain and exhibits an unusual ability to hydrolyze β-1,3-galactan in the presence of a β-1,6 linked branch. Here, we present its crystal structure at 2.7 Å resolution and complex structures of the enzyme with several substrates and analogs. Two modes of substrate binding were observed at the β site of the CtCBM13 domain, and one galactobiose molecule was found in an "L" shaped pocket of the CtGH43 domain, which appears large enough to accommodate two more galactose units. In addition, we found that mutating Glu112 to Gln or Ala eliminated the galactan hydrolysis activity of Ct1,3Gal43A while did not disrupt its ligand binding ability. Combining this results and the crystal structure we identified Glu112 in Ct1,3Gal43A as the 'missing' essential acidic residue in galactan β-1,3-galactosidases. Structural information presented here also suggests a mechanism by which Ct1,3Gal43A bypasses β-1,6 linked branches in the substrate and another mechanism by which the substrate is delivered 'in trans' from the CBM13 domain to the catalytic GH43 domain.

PubMed: 22960181
DOI: 10.1016/j.jsb.2012.08.005

実験手法

X-RAY DIFFRACTION (2.913 Å)