5G56

THE TETRA-MODULAR CELLULOSOMAL ARABINOXYLANASE CtXyl5A STRUCTURE AS REVEALED BY X-RAY CRYSTALLOGRAPHY

「5AK1」から置き換えられました

5G56 の概要

• エントリーDOI: 10.2210/pdb5g56/pdb
• 分子名称: CARBOHYDRATE BINDING FAMILY 6, CALCIUM ION, (4S)-2-METHYL-2,4-PENTANEDIOL, ... (4 entities in total)
• 機能のキーワード: carbohydrate binding protein, arabinoxylanase, ctxyl5a, gh5, cbm6, cbm13, fn3, clostridium thermocellum, cellulosome
• 由来する生物種: CLOSTRIDIUM THERMOCELLUM
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 94306.23

構造登録者

Bras, J.L.A.,Gilbert, H.J.,Ferreira, L.M.A.,Fontes, C.M.G.A.,Najmudin, S. (登録日: 2016-05-21, 公開日: 2016-06-29, 最終更新日: 2024-10-23)

主引用文献

Labourel, A.,Crouch, L.I.,Bras, J.L.,Jackson, A.,Rogowski, A.,Gray, J.,Yadav, M.P.,Henrissat, B.,Fontes, C.M.,Gilbert, H.J.,Najmudin, S.,Basle, A.,Cuskin, F.
The Mechanism by which Arabinoxylanases Can Recognise Highly Decorated Xylans.
J.Biol.Chem., 291:22149-, 2016

PubMed Abstract: The enzymatic degradation of plant cell walls is an important biological process of increasing environmental and industrial significance. Xylan, a major component of the plant cell wall, consists of a backbone of β-1,4-xylose (Xylp) units that are often decorated with arabinofuranose (Araf) side chains. A large penta-modular enzyme, CtXyl5A, was shown previously to specifically target arabinoxylans. The mechanism of substrate recognition displayed by the enzyme, however, remains unclear. Here we report the crystal structure of the arabinoxylanase and the enzyme in complex with ligands. The data showed that four of the protein modules adopt a rigid structure, which stabilizes the catalytic domain. The C-terminal non-catalytic carbohydrate binding module could not be observed in the crystal structure, suggesting positional flexibility. The structure of the enzyme in complex with Xylp-β-1,4-Xylp-β-1,4-Xylp-[α-1,3-Araf]-β-1,4-Xylp showed that the Araf decoration linked O to the xylose in the active site is located in the pocket (-2* subsite) that abuts onto the catalytic center. The -2* subsite can also bind to Xylp and Arap, explaining why the enzyme can utilize xylose and arabinose as specificity determinants. Alanine substitution of Glu, Tyr, or Asn, which interact with arabinose and xylose side chains at the -2* subsite, abrogates catalytic activity. Distal to the active site, the xylan backbone makes limited apolar contacts with the enzyme, and the hydroxyls are solvent-exposed. This explains why CtXyl5A is capable of hydrolyzing xylans that are extensively decorated and that are recalcitrant to classic endo-xylanase attack.

PubMed: 27531750
DOI: 10.1074/JBC.M116.743948

実験手法

X-RAY DIFFRACTION (2.64 Å)