Experimental Data Snapshot

  • Resolution: 1.45 Å
  • R-Value Free: 0.221 
  • R-Value Work: 0.203 

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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

  • DOI: https://doi.org/10.1021/bi015621z
  • Primary Citation of Related Structures:  
    1I86, 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 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.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B
389Medicago sativaMutation(s): 2 
Find proteins for P30074 (Medicago sativa)
Explore P30074 
Go to UniProtKB:  P30074
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP30074
Sequence Annotations
  • Reference Sequence
Small Molecules
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
Query on CSD
A, B
Experimental Data & Validation

Experimental Data

  • Resolution: 1.45 Å
  • R-Value Free: 0.221 
  • R-Value Work: 0.203 
  • Space Group: P 31 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 98.292α = 90
b = 98.292β = 90
c = 129.676γ = 120
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2001-12-12
    Type: Initial release
  • Version 1.1: 2008-04-27
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Derived calculations, Version format compliance
  • Version 1.3: 2021-10-27
    Changes: Database references, Derived calculations