Experimental Data Snapshot

  • Method: SOLUTION NMR
  • Conformers Calculated: 30 
  • Conformers Submitted: 30 

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Solution Structure of the Squash Trypsin Inhibitor Mcoti-II. A New Family for Cyclic Knottins

Heitz, A.Hernandez, J.-F.Gagnon, J.Hong, T.T.Pham, T.T.C.Nguyen, T.M.Le-Nguyen, D.Chiche, L.

(2001) Biochemistry 40: 7973

  • DOI: https://doi.org/10.1021/bi0106639
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    The "knottin" fold is a stable cysteine-rich scaffold, in which one disulfide crosses the macrocycle made by two other disulfides and the connecting backbone segments. This scaffold is found in several protein families with no evolutionary relationships. In the past few years, several homologous peptides from the Rubiaceae and Violaceae families were shown to define a new structural family based on macrocyclic knottin fold. We recently isolated from Momordica cochinchinensis seeds the first known macrocyclic squash trypsin inhibitors. These compounds are the first members of a new family of cyclic knottins. In this paper, we present NMR structural studies of one of them, MCoTI-II, and of a beta-Asp rearranged form, MCoTI-IIb. Both compounds display similar and well-defined conformations. These cyclic squash inhibitors share a similar conformation with noncyclic squash inhibitors such as CPTI-II, and it is postulated that the main effect of the cyclization is a reduced sensitivity to exo-proteases. On the contrary, clear differences were detected with the three-dimensional structures of other known cyclic knottins, i.e., kalata B1 or circulin A. The two-disulfide cystine-stabilized beta-sheet motif [Heitz et al. (1999) Biochemistry 38, 10615-10625] is conserved in the two families, whereas in the C-to-N linker, one disulfide bridge and one loop are differently located. The molecular surface of MCoTI-II is almost entirely charged in contrast to circulin A that displays a well-marked amphiphilic character. These differences might explain why the isolated macrocyclic squash inhibitors from M. cochinchinensis display no significant antibacterial activity, whereas circulins and kalata B1 do.

  • Organizational Affiliation

    Centre de Biochimie Structurale, UMR5048 CNRS-Université Montpellier I, UMR554 INSERM-Université Montpellier I, Faculté de pharmacie, 15 avenue Charles Flahault, 34060 Montpellier, France.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
TRYPSIN INHIBITOR II34Momordica cochinchinensisMutation(s): 0 
Find proteins for P82409 (Momordica cochinchinensis)
Explore P82409 
Go to UniProtKB:  P82409
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP82409
Sequence Annotations
  • Reference Sequence
Biologically Interesting Molecules (External Reference) 1 Unique
Experimental Data & Validation

Experimental Data

  • Method: SOLUTION NMR
  • Conformers Calculated: 30 
  • Conformers Submitted: 30 

Structure Validation

View Full Validation Report

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2001-04-12
    Type: Initial release
  • Version 1.1: 2012-11-30
    Changes: Other
  • Version 1.2: 2020-01-15
    Changes: Data collection, Other
  • Version 1.3: 2023-06-14
    Changes: Database references, Other