5GQU

Crystal structure of branching enzyme from Cyanothece sp. ATCC 51142

5GQU の概要

• エントリーDOI: 10.2210/pdb5gqu/pdb
• 関連するPDBエントリー: 5GQV 5GQW 5GQX 5GQY 5GQZ 5GR0 5GR1 5GR2 5GR3 5GR4 5GR5 5GR6
• 分子名称: 1,4-alpha-glucan branching enzyme GlgB, GLYCEROL, MAGNESIUM ION, ... (4 entities in total)
• 機能のキーワード: branching enzyme, glycoside hydrolase family 13, cyanobacteria, starch, transferase
• 由来する生物種: Cyanothece sp. (strain ATCC 51142)
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 93428.30

構造登録者

Suzuki, R.,Suzuki, E. (登録日: 2016-08-08, 公開日: 2017-02-22, 最終更新日: 2023-11-08)

主引用文献

Hayashi, M.,Suzuki, R.,Colleoni, C.,Ball, S.G.,Fujita, N.,Suzuki, E.
Bound Substrate in the Structure of Cyanobacterial Branching Enzyme Supports a New Mechanistic Model
J. Biol. Chem., 292:5465-5475, 2017

PubMed Abstract: Branching enzyme (BE) catalyzes the formation of α-1,6-glucosidic linkages in amylopectin and glycogen. The reaction products are variable, depending on the organism sources, and the mechanistic basis for these different outcomes is unclear. Although most cyanobacteria have only one BE isoform belonging to glycoside hydrolase family 13, sp. ATCC 51142 has three isoforms (BE1, BE2, and BE3) with distinct enzymatic properties, suggesting that investigations of these enzymes might provide unique insights into this system. Here, we report the crystal structure of ligand-free wild-type BE1 (residues 5-759 of 1-773) at 1.85 Å resolution. The enzyme consists of four domains, including domain N, carbohydrate-binding module family 48 (CBM48), domain A containing the catalytic site, and domain C. The central domain A displays a (β/α)-barrel fold, whereas the other domains adopt β-sandwich folds. Domain N was found in a new location at the back of the protein, forming hydrogen bonds and hydrophobic interactions with CBM48 and domain A. Site-directed mutational analysis identified a mutant (W610N) that bound maltoheptaose with sufficient affinity to enable structure determination at 2.30 Å resolution. In this structure, maltoheptaose was bound in the active site cleft, allowing us to assign subsites -7 to -1. Moreover, seven oligosaccharide-binding sites were identified on the protein surface, and we postulated that two of these in domain A served as the entrance and exit of the donor/acceptor glucan chains, respectively. Based on these structures, we propose a substrate binding model explaining the mechanism of glycosylation/deglycosylation reactions catalyzed by BE.

PubMed: 28193843
DOI: 10.1074/jbc.M116.755629

実験手法

X-RAY DIFFRACTION (1.85 Å)