3AXI

Crystal structure of isomaltase in complex with maltose


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.4 Å
  • R-Value Free: 0.194 
  • R-Value Work: 0.179 

wwPDB Validation 3D Report Full Report


This is version 1.1 of the entry. See complete history

Literature

Steric hindrance by 2 amino acid residues determines the substrate specificity of isomaltase from Saccharomyces cerevisiae

Yamamoto, K.Miyake, H.Kusunoki, M.Osaki, S.

(2011) J.Biosci.Bioeng. 112: 545-550

  • DOI: 10.1016/j.jbiosc.2011.08.016
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • The structures of the E277A isomaltase mutant from Saccharomyces cerevisiae in complex with isomaltose or maltose were determined at resolutions of 1.80 and 1.40Å, respectively. The root mean square deviations between the corresponding main-chain ato ...

    The structures of the E277A isomaltase mutant from Saccharomyces cerevisiae in complex with isomaltose or maltose were determined at resolutions of 1.80 and 1.40Å, respectively. The root mean square deviations between the corresponding main-chain atoms of free isomaltase and the E277Α-isomaltose complex structures and those of free isomaltase and the E277A-maltose complex structures were found to be 0.131Å and 0.083Å, respectively. Thus, the amino acid substitution and ligand binding do not affect the overall structure of isomaltase. In the E277A-isomaltose structure, the bound isomaltose was readily identified by electron densities in the active site pocket; however, the reducing end of maltose was not observed in the E277A-maltose structure. The superposition of maltose onto the E277A-maltose structure revealed that the reducing end of maltose cannot bind to the subsite +1 due to the steric hindrance from Val216 and Gln279. The amino acid sequence comparisons with α-glucosidases showed that a bulky hydrophobic amino acid residue is conserved at the position of Val216 in α-1,6-glucosidic linkage hydrolyzing enzymes. Similarly, a bulky amino acid residue is conserved at the position of Gln279 in α-1,6-glucosidic linkage-only hydrolyzing α-glucosidases. Ala, Gly, or Asn residues were located at the position of α-1,4-glucosidic linkage hydrolyzing α-glucosidases. Two isomaltase mutant enzymes - V216T and Q279A - hydrolyzed maltose. Thus, the amino acid residues at these positions may be largely responsible for determining the substrate specificity of α-glucosidases.


    Organizational Affiliation

    School of Medicine, Nara Medical University, 840 Shijo, Kashihara, Nara 634-8521, Japan. kama@naramed-u.ac.jp




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Oligo-1,6-glucosidase IMA1
A
589Saccharomyces cerevisiae (strain ATCC 204508 / S288c)Mutation(s): 1 
Gene Names: IMA1
EC: 3.2.1.10
Find proteins for P53051 (Saccharomyces cerevisiae (strain ATCC 204508 / S288c))
Go to UniProtKB:  P53051
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
CA
Query on CA

Download SDF File 
Download CCD File 
A
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
GLC
Query on GLC

Download SDF File 
Download CCD File 
A
ALPHA-D-GLUCOSE
C6 H12 O6
WQZGKKKJIJFFOK-DVKNGEFBSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.4 Å
  • R-Value Free: 0.194 
  • R-Value Work: 0.179 
  • Space Group: C 1 2 1
Unit Cell:
Length (Å)Angle (°)
a = 95.474α = 90.00
b = 115.373β = 91.07
c = 61.594γ = 90.00
Software Package:
Software NamePurpose
MOLREPphasing
REFMACrefinement
HKL-2000data scaling
HKL-2000data reduction
HKL-2000data collection

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2011-10-05
    Type: Initial release
  • Version 1.1: 2013-06-19
    Type: Database references