9D0Z

X-ray crystal structure of H157Q variant Thermothelomyces thermophilus polysaccharide monooxygenase 9E

9D0Z の概要

• エントリーDOI: 10.2210/pdb9d0z/pdb
• 分子名称: Glycoside hydrolase family 61 protein, COPPER (II) ION, OXYGEN MOLECULE, ... (5 entities in total)
• 機能のキーワード: polysaccharide monooxygenase, oxidoreductase
• 由来する生物種: Thermothelomyces thermophilus
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 49014.99

構造登録者

Thomas, W.C.,Batka, A.E.,Marletta, M.A. (登録日: 2024-08-07, 公開日: 2024-12-04, 最終更新日: 2024-12-18)

主引用文献

Batka, A.E.,Thomas, W.C.,Tudorica, D.A.,Sayler, R.I.,Marletta, M.A.
Second-Sphere Histidine Catalytic Function in a Fungal Polysaccharide Monooxygenase.
Biochemistry, 63:3136-3146, 2024

PubMed Abstract: Fungal polysaccharide monooxygenases (PMOs) oxidatively degrade cellulose and other carbohydrate polymers via a mononuclear copper active site using either O or HO as a cosubstrate. Cellulose-active fungal PMOs in the auxiliary activity 9 (AA9) family have a conserved second-sphere hydrogen-bonding network consisting of histidine, glutamine, and tyrosine residues. The second-sphere histidine has been hypothesized to play a role in proton transfer in the O-dependent PMO reaction. Here the role of the second-sphere histidine (H157) in an AA9 PMO, PMO9E, was investigated. This PMO is active on soluble cello-oligosaccharides such as cellohexaose (Glc6), thus enabling kinetic analysis with the point variants H157A and H157Q. The variants appeared to fold similarly to the wild-type (WT) enzyme and yet exhibited weaker affinity toward Glc6 than WT (WT = 20 ± 3 μM). The variants had comparable oxidase (O reduction to HO) activity to WT at all pH values tested. Using O as a cosubstrate, the variants were less active for Glc6 hydroxylation than WT, with H157A being the least active. Similarly, H157Q was competent for Glc6 hydroxylation with HO, but H157A was less active. Comparison of the crystal structures of H157Q and WT PMO9E reveals that a terminal heteroatom of Q157 overlays with N of H157. Altogether, the data suggest that H157 is not important for proton transfer, but support a role for H157 as a hydrogen-bond donor to diatomic-oxygen intermediates, thus facilitating catalysis with either O or HO.

PubMed: 39563485
DOI: 10.1021/acs.biochem.4c00527

実験手法

X-RAY DIFFRACTION (1.8 Å)