1I86

CHALCONE SYNTHASE, G256A MUTANT


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.5 Å
  • R-Value Free: 0.221 
  • R-Value Work: 0.187 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Structure-guided programming of polyketide chain-length determination in chalcone synthase.

Jez, J.M.Bowman, M.E.Noel, J.P.

(2001) Biochemistry 40: 14829-14838

  • Primary Citation of Related Structures:  1I88, 1I89, 1I8B

  • PubMed Abstract: 
  • Chalcone synthase (CHS) belongs to the family of type III polyketide synthases (PKS) that catalyze formation of structurally diverse polyketides. CHS synthesizes a tetraketide by sequential condensation of three acetyl anions derived from malonyl-CoA ...

    Chalcone synthase (CHS) belongs to the family of type III polyketide synthases (PKS) that catalyze formation of structurally diverse polyketides. CHS synthesizes a tetraketide by sequential condensation of three acetyl anions derived from malonyl-CoA decarboxylation to a p-coumaroyl moiety attached to an active site cysteine. Gly256 resides on the surface of the CHS active site that is in direct contact with the polyketide chain derived from malonyl-CoA. Thus, position 256 serves as an ideal target to probe the link between cavity volume and polyketide chain-length determination in type III PKS. Functional examination of CHS G256A, G256V, G256L, and G256F mutants reveals altered product profiles from that of wild-type CHS. With p-coumaroyl-CoA as a starter molecule, the G256A and G256V mutants produce notably more tetraketide lactone. Further restrictions in cavity volume such as that seen in the G256L and G256F mutants yield increasing levels of the styrylpyrone bis-noryangonin from a triketide intermediate. X-ray crystallographic structures of the CHS G256A, G256V, G256L, and G256F mutants establish that these substitutions reduce the size of the active site cavity without significant alterations in the conformations of the polypeptide backbones. The side chain volume of position 256 influences both the number of condensation reactions during polyketide chain extension and the conformation of the triketide and tetraketide intermediates during the cyclization reaction. These results viewed in conjunction with the natural sequence variation of residue 256 suggest that rapid diversification of product specificity without concomitant loss of substantial catalytic activity in related CHS-like enzymes can occur by site-specific evolution of side chain volume at position 256.


    Organizational Affiliation

    Structural Biology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
CHALCONE SYNTHASE 2
A
389Medicago sativaGene Names: CHS2
EC: 2.3.1.74
Find proteins for P30074 (Medicago sativa)
Go to UniProtKB:  P30074
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
SO4
Query on SO4

Download SDF File 
Download CCD File 
A
SULFATE ION
O4 S
QAOWNCQODCNURD-UHFFFAOYSA-L
 Ligand Interaction
Modified Residues  1 Unique
IDChainsTypeFormula2D DiagramParent
CSD
Query on CSD
A
L-PEPTIDE LINKINGC3 H7 N O4 SCYS
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.5 Å
  • R-Value Free: 0.221 
  • R-Value Work: 0.187 
  • Space Group: P 32 2 1
Unit Cell:
Length (Å)Angle (°)
a = 98.096α = 90.00
b = 98.096β = 90.00
c = 65.066γ = 120.00
Software Package:
Software NamePurpose
REFMACrefinement
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2001-12-12
    Type: Initial release
  • Version 1.1: 2008-04-27
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Derived calculations, Version format compliance