4S3P

Amylomaltase MalQ from Escherichia coli, apo structure

4S3P の概要

• エントリーDOI: 10.2210/pdb4s3p/pdb
• 関連するPDBエントリー: 4S3Q 4S3R
• 分子名称: 4-alpha-glucanotransferase (2 entities in total)
• 機能のキーワード: glucoside hydrolase clan h, maltose, maltodextrin, tim barrel, transferase
• 由来する生物種: Escherichia coli K-12
• 細胞内の位置: Cytoplasm: P15977
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 157965.33

構造登録者

Weiss, S.C.,Schiefner, A. (登録日: 2015-03-26, 公開日: 2015-07-08, 最終更新日: 2023-09-20)

主引用文献

Weiss, S.C.,Skerra, A.,Schiefner, A.
Structural Basis for the Interconversion of Maltodextrins by MalQ, the Amylomaltase of Escherichia coli.
J.Biol.Chem., 290:21352-21364, 2015

PubMed Abstract: Amylomaltase MalQ is essential for the metabolism of maltose and maltodextrins in Escherichia coli. It catalyzes transglycosylation/disproportionation reactions in which glycosyl or dextrinyl units are transferred among linear maltodextrins of various lengths. To elucidate the molecular basis of transglycosylation by MalQ, we have determined three crystal structures of this enzyme, i.e. the apo-form, its complex with maltose, and an inhibitor complex with the transition state analog acarviosine-glucose-acarbose, at resolutions down to 2.1 Å. MalQ represents the first example of a mesophilic bacterial amylomaltase with known structure and exhibits an N-terminal extension of about 140 residues, in contrast with previously described thermophilic enzymes. This moiety seems unique to amylomaltases from Enterobacteriaceae and folds into two distinct subdomains that associate with different parts of the catalytic core. Intriguingly, the three MalQ crystal structures appear to correspond to distinct states of this enzyme, revealing considerable conformational changes during the catalytic cycle. In particular, the inhibitor complex highlights the requirement of both a 3-OH group and a 4-OH group (or α1-4-glycosidic bond) at the acceptor subsite +1 for the catalytically competent orientation of the acid/base catalyst Glu-496. Using an HPLC-based MalQ enzyme assay, we could demonstrate that the equilibrium concentration of maltodextrin products depends on the length of the initial substrate; with increasing numbers of glycosidic bonds, less glucose is formed. Thus, both structural and enzymatic data are consistent with the extremely low hydrolysis rates observed for amylomaltases and underline the importance of MalQ for the metabolism of maltodextrins in E. coli.

PubMed: 26139606
DOI: 10.1074/jbc.M115.667337

実験手法

X-RAY DIFFRACTION (2.8 Å)