4S3P

Amylomaltase MalQ from Escherichia coli, apo structure


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.8 Å
  • R-Value Free: 0.224 
  • R-Value Work: 0.180 

wwPDB Validation 3D Report Full Report


This is version 1.3 of the entry. See complete history

Literature

Structural Basis for the Interconversion of Maltodextrins by MalQ, the Amylomaltase of Escherichia coli.

Weiss, S.C.Skerra, A.Schiefner, A.

(2015) J.Biol.Chem. 290: 21352-21364

  • DOI: 10.1074/jbc.M115.667337
  • Primary Citation of Related Structures:  

  • 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 variou ...

    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.


    Organizational Affiliation

    From the Lehrstuhl für Biologische Chemie, Technische Universität München, Emil-Erlenmeyer-Forum 5, 85350 Freising-Weihenstephan, Germany.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
4-alpha-glucanotransferase
A, B
696Escherichia coli (strain K12)Mutation(s): 0 
Gene Names: malQ (malA)
EC: 2.4.1.25
Find proteins for P15977 (Escherichia coli (strain K12))
Go to UniProtKB:  P15977
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.8 Å
  • R-Value Free: 0.224 
  • R-Value Work: 0.180 
  • Space Group: P 2 2 21
Unit Cell:
Length (Å)Angle (°)
a = 85.337α = 90.00
b = 106.811β = 90.00
c = 217.665γ = 90.00
Software Package:
Software NamePurpose
PDB_EXTRACTdata extraction
PHASERphasing
XSCALEdata scaling
XDSdata reduction
REFMACrefinement
MAR345data collection

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2015-07-08
    Type: Initial release
  • Version 1.1: 2015-07-15
    Type: Database references
  • Version 1.2: 2015-09-16
    Type: Database references
  • Version 1.3: 2017-11-22
    Type: Refinement description