1J18

Crystal Structure of a Beta-Amylase from Bacillus cereus var. mycoides Cocrystallized with Maltose

1J18 の概要

• エントリーDOI: 10.2210/pdb1j18/pdb
• 関連するPDBエントリー: 5BCA
• 関連するBIRD辞書のPRD_ID: PRD_900010 PRD_900018
• 分子名称: Beta-amylase, alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose-(1-4)-alpha-D-glucopyranose, alpha-D-glucopyranose-(1-4)-beta-D-glucopyranose, ... (7 entities in total)
• 機能のキーワード: beta-amylase, amylase, complex, tim barel, maltose, hydrolase
• 由来する生物種: Bacillus cereus
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 59905.89

構造登録者

Miyake, H.,Kurisu, G.,Kusunoki, M.,Nishimura, S.,Kitamura, S.,Nitta, Y. (登録日: 2002-12-02, 公開日: 2003-05-27, 最終更新日: 2024-11-20)

主引用文献

Miyake, H.,Kurisu, G.,Kusunoki, M.,Nishimura, S.,Kitamura, S.,Nitta, Y.
Crystal Structure of a Catalytic Site Mutant of beta-Amylase from Bacillus cereus var. mycoides Cocrystallized with Maltopentaose
BIOCHEMISTRY, 42:5574-5581, 2003

PubMed Abstract: The X-ray crystal structure of a catalytic site mutant of beta-amylase, E172A (Glu172 --> Ala), from Bacillus cereus var. mycoides complexed with a substrate, maltopentaose (G5), and the wild-type enzyme complexed with maltose were determined at 2.1 and 2.0 A resolution, respectively. Clear and continuous density corresponding to G5 was observed in the active site of E172A, and thus, the substrate, G5, was not hydrolyzed. All glucose residues adopted a relaxed (4)C(1) conformation, and the conformation of the maltose unit for Glc2 and Glc3 was much different from those of other maltose units, where each glucose residue of G5 is named Glc1-Glc5 (Glc1 is at the nonreducing end). A water molecule was observed 3.3 A from the C1 atom of Glc2, and 3.0 A apart from the OE1 atom of Glu367 which acts as a general base. In the wild-type enzyme-maltose complex, two maltose molecules bind at subsites -2 and -1 and at subsites +1 and +2 in tandem. The conformation of the maltose molecules was similar to that of the condensation product of soybean beta-amylase, but differed from that of G5 in E172A. When the substrate flips between Glc2 and Glc3, the conformational energy of the maltose unit was calculated to be 20 kcal/mol higher than that of the cis conformation by MM3. We suggest that beta-amylase destabilizes the bond that is to be broken in the ES complex, decreasing the activation energy, DeltaG(++), which is the difference in free energy between this state and the transition state.

PubMed: 12741813
DOI: 10.1021/bi020712x

実験手法

X-RAY DIFFRACTION (2 Å)