1B1Y

SEVENFOLD MUTANT OF BARLEY BETA-AMYLASE

1B1Y の概要

• エントリーDOI: 10.2210/pdb1b1y/pdb
• 関連するBIRD辞書のPRD_ID: PRD_900018
• 分子名称: PROTEIN (BETA-AMYLASE), alpha-D-glucopyranose-(1-4)-beta-D-glucopyranose, beta-D-glucopyranose, ... (4 entities in total)
• 機能のキーワード: hydrolase(o-glycosyl), hydrolase
• 由来する生物種: Hordeum vulgare
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 56839.78

構造登録者

Mikami, B.,Yoon, H.J.,Yoshigi, N. (登録日: 1998-11-25, 公開日: 1998-12-02, 最終更新日: 2023-08-09)

主引用文献

Mikami, B.,Yoon, H.J.,Yoshigi, N.
The crystal structure of the sevenfold mutant of barley beta-amylase with increased thermostability at 2.5 A resolution.
J.Mol.Biol., 285:1235-1243, 1999

PubMed Abstract: The three-dimensional structure of the sevenfold mutant of barley beta-amylase (BBA-7s) with increased thermostability was determined by X-ray crystallography. The enzyme was purified as a single component and crystallized by a hanging drop method in the presence of 14 % PEG 6000. The crystals belong to space group P43212 with cell dimensions a=b=72.11 A, c=250.51 A. The diffraction data up to 2.5 A were collected after soaking the crystal in 100 mM maltose with Rsym of 8.6 %. The structure was determined by a molecular replacement method using soybean beta-amylase (SBA) as a search model and refined to an R-factor of 18.7 %. The final model included 500 amino acid residues, 141 water molecules and three glucose residues, which were located at subsites 1-2 and 4 in the active site. The r.m.s. distance of 485 Calpha atoms between BBA-7s and SBA was 0.62 A. Out of the seven mutated amino acids, four (Ser295Ala, Ile297Val, Ser351Pro and Ala376Ser) were substitutions from the common residues with SBA to the thermostable forms. A comparison of the structures of BBA-7s and SBA indicated that the side-chain of Ser376 makes new hydrogen bonds to the main-chain of an adjacent beta-strand, and that the side-chains of Val297 reduce an unfavorable interaction between the side-chains of Ala314. The mutation of Ser295Ala breaks the hydrogen bond between Ser295 OG and Tyr195 OH, which seems to be the reason for the unoccupied glucose residue at subsite 3. The tandem mutations at 350-352 including substitutions to two Pro residues suggested the reduction of main-chain entropy in the unfolded structure of this solvent-exposed protruded loop.

PubMed: 9918723
DOI: 10.1006/jmbi.1998.2379

実験手法

X-RAY DIFFRACTION (2.5 Å)