6RWF

The dissociation mechanism of processive cellulases

6RWF の概要

• エントリーDOI: 10.2210/pdb6rwf/pdb
• 分子名称: Glucanase, COBALT (II) ION, 2-acetamido-2-deoxy-beta-D-glucopyranose, ... (4 entities in total)
• 機能のキーワード: cellobiogydrolase i, cel7a from hypocrea jecorina, hydrolase
• 由来する生物種: Hypocrea jecorina (strain QM6a)
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 46324.46

構造登録者

Stahlberg, J.,Knott, B.C. (登録日: 2019-06-04, 公開日: 2019-11-06, 最終更新日: 2024-11-06)

主引用文献

Vermaas, J.V.,Kont, R.,Beckham, G.T.,Crowley, M.F.,Gudmundsson, M.,Sandgren, M.,Stahlberg, J.,Valjamae, P.,Knott, B.C.
The dissociation mechanism of processive cellulases.
Proc.Natl.Acad.Sci.USA, 116:23061-23067, 2019

PubMed Abstract: Cellulase enzymes deconstruct recalcitrant cellulose into soluble sugars, making them a biocatalyst of biotechnological interest for use in the nascent lignocellulosic bioeconomy. Cellobiohydrolases (CBHs) are cellulases capable of liberating many sugar molecules in a processive manner without dissociating from the substrate. Within the complete processive cycle of CBHs, dissociation from the cellulose substrate is rate limiting, but the molecular mechanism of this step is unknown. Here, we present a direct comparison of potential molecular mechanisms for dissociation via Hamiltonian replica exchange molecular dynamics of the model fungal CBH, Cel7A. Computational rate estimates indicate that stepwise cellulose dethreading from the binding tunnel is 4 orders of magnitude faster than a clamshell mechanism, in which the substrate-enclosing loops open and release the substrate without reversing. We also present the crystal structure of a disulfide variant that covalently links substrate-enclosing loops on either side of the substrate-binding tunnel, which constitutes a CBH that can only dissociate via stepwise dethreading. Biochemical measurements indicate that this variant has a dissociation rate constant essentially equivalent to the wild type, implying that dethreading is likely the predominant mechanism for dissociation.

PubMed: 31666327
DOI: 10.1073/pnas.1913398116

実験手法

X-RAY DIFFRACTION (1.64 Å)