4OKD

Crystal Structure of Chlamydomonas reinhardtii Isoamylase 1 (ISA1) in complex with maltoheptaose


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.4 Å
  • R-Value Free: 0.227 
  • R-Value Work: 0.192 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Crystal Structure of the Chlamydomonas Starch Debranching Enzyme Isoamylase ISA1 Reveals Insights into the Mechanism of Branch Trimming and Complex Assembly.

Sim, L.Beeren, S.R.Findinier, J.Dauvillee, D.Ball, S.G.Henriksen, A.Palcic, M.M.

(2014) J.Biol.Chem. 289: 22991-23003

  • DOI: 10.1074/jbc.M114.565044
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • The starch debranching enzymes isoamylase 1 and 2 (ISA1 and ISA2) are known to exist in a large complex and are involved in the biosynthesis and crystallization of starch. It is suggested that the function of the complex is to remove misplaced branch ...

    The starch debranching enzymes isoamylase 1 and 2 (ISA1 and ISA2) are known to exist in a large complex and are involved in the biosynthesis and crystallization of starch. It is suggested that the function of the complex is to remove misplaced branches of growing amylopectin molecules, which would otherwise prevent the association and crystallization of adjacent linear chains. Here, we investigate the function of ISA1 and ISA2 from starch producing alga Chlamydomonas. Through complementation studies, we confirm that the STA8 locus encodes for ISA2 and sta8 mutants lack the ISA1·ISA2 heteromeric complex. However, mutants retain a functional dimeric ISA1 that is able to partly sustain starch synthesis in vivo. To better characterize ISA1, we have overexpressed and purified ISA1 from Chlamydomonas reinhardtii (CrISA1) and solved the crystal structure to 2.3 Å and in complex with maltoheptaose to 2.4 Å. Analysis of the homodimeric CrISA1 structure reveals a unique elongated structure with monomers connected end-to-end. The crystal complex reveals details about the mechanism of branch binding that explains the low activity of CrISA1 toward tightly spaced branches and reveals the presence of additional secondary surface carbohydrate binding sites.


    Organizational Affiliation

    From the Carlsberg Laboratory, Gamle Carlsberg Vej 10, DK-1799 Copenhagen V, Denmark and lya.sim@gmail.com.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Isoamylase
A, B
840Chlamydomonas reinhardtiiMutation(s): 0 
Gene Names: Isa1
Find proteins for Q7X8Q2 (Chlamydomonas reinhardtii)
Go to UniProtKB:  Q7X8Q2
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
GLC
Query on GLC

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

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.4 Å
  • R-Value Free: 0.227 
  • R-Value Work: 0.192 
  • Space Group: P 41 21 2
Unit Cell:
Length (Å)Angle (°)
a = 102.750α = 90.00
b = 102.750β = 90.00
c = 487.810γ = 90.00
Software Package:
Software NamePurpose
PDB_EXTRACTdata extraction
XDSdata reduction
XSCALEdata scaling
REFMACrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

  • Deposited Date: 2014-01-22 
  • Released Date: 2014-07-02 
  • Deposition Author(s): Sim, L., Palcic, M.

Revision History 

  • Version 1.0: 2014-07-02
    Type: Initial release
  • Version 1.1: 2014-07-23
    Type: Database references
  • Version 1.2: 2014-09-03
    Type: Database references