Solution structure of the cyclotide cycloviolacin O2 with Glu6 methylated (cyO2Me)

Experimental Data Snapshot

  • Method: SOLUTION NMR
  • Conformers Calculated: 50 
  • Conformers Submitted: 20 
  • Selection Criteria: structures with the lowest energy 

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The conserved glu in the cyclotide cycloviolacin O2 has a key structural role.

Goransson, U.Herrmann, A.Burman, R.Haugaard-Jonsson, L.M.Rosengren, K.J.

(2009) Chembiochem 10: 2354-2360

  • DOI: https://doi.org/10.1002/cbic.200900342
  • Primary Citation of Related Structures:  
    2KNM, 2KNN

  • PubMed Abstract: 

    Cyclotides are a large family of plant peptides that are characterised by a head-to-tail circular backbone and three disulfide bonds that are arranged in a cystine knot. This unique structural feature, which is referred to as a cyclic cystine knot, gives the cyclotides remarkable stability against chemical and biological degradation. In addition to their natural function as insecticides for plant defence, the cyclotides have a range of bioactivities with pharmaceutical relevance, including cytotoxicity against cancer cell lines. A glutamic acid residue, aside from the invariable disulfide array, is the most conserved feature throughout the cyclotide family, and it has recently been shown to be crucial for biological activity. Here we have used solution-state NMR spectroscopy to determine the three-dimensional structures of the potent cytotoxic cyclotide cycloviolacin O2, and an inactive analogue in which this conserved glutamic acid has been methylated. The structures of the peptides show that the glutamic acid has a key structural role in coordinating a set of hydrogen bonds in native cycloviolacin O2; this interaction is disrupted in the methylated analogue. The proposed mechanism of action of cyclotides is membrane disruption and these results suggest that the glutamic acid is linked to cyclotide function by stabilising the structure to allow efficient aggregation in membranes, rather than in a direct interaction with a target receptor.

  • Organizational Affiliation

    Division of Pharmacognosy, Department of Medicinal Chemistry, Biomedical Centre, Uppsala University, 751 23 Uppsala, Sweden.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Cycloviolacin-O230Viola odorataMutation(s): 0 
Find proteins for P58434 (Viola odorata)
Explore P58434 
Go to UniProtKB:  P58434
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP58434
Sequence Annotations
  • Reference Sequence
Small Molecules
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
Query on GME
Experimental Data & Validation

Experimental Data

  • Method: SOLUTION NMR
  • Conformers Calculated: 50 
  • Conformers Submitted: 20 
  • Selection Criteria: structures with the lowest energy 

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2010-03-09
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2022-03-16
    Changes: Data collection, Database references, Derived calculations