Solution structure of SFTI-1(6,5), an acyclic permutant of the proteinase inhibitor SFTI-1, trans-trans-trans conformer (tt-A)

Experimental Data Snapshot

  • Method: SOLUTION NMR
  • Conformers Calculated: 50 
  • Conformers Submitted: 20 
  • Selection Criteria: LEAST OVERALL ENERGIES 

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Enzymatic Cyclization of a Potent Bowman-Birk Protease Inhibitor, Sunflower Trypsin Inhibitor-1, and Solution Structure of an Acyclic Precursor Peptide

Marx, U.C.Korsinczky, M.Schirra, H.Jones, A.Condie, B.Otvos, L.Craik, D.J.

(2003) J Biol Chem 278: 21782

  • DOI: https://doi.org/10.1074/jbc.M212996200
  • Primary Citation of Related Structures:  
    1O8Y, 1O8Z

  • PubMed Abstract: 

    The most potent known naturally occurring Bowman-Birk inhibitor, sunflower trypsin inhibitor-1 (SFTI-1), is a bicyclic 14-amino acid peptide from sunflower seeds comprising one disulfide bond and a cyclic backbone. At present, little is known about the cyclization mechanism of SFTI-1. We show here that an acyclic permutant of SFTI-1 open at its scissile bond, SFTI-1[6,5], also functions as an inhibitor of trypsin and that it can be enzymatically backbone-cyclized by incubation with bovine beta-trypsin. The resulting ratio of cyclic SFTI-1 to SFTI-1[6,5] is approximately 9:1 regardless of whether trypsin is incubated with SFTI-1[6,5] or SFTI-1. Enzymatic resynthesis of the scissile bond to form cyclic SFTI-1 is a novel mechanism of cyclization of SFTI-1[6,5]. Such a reaction could potentially occur on a trypsin affinity column as used in the original isolation procedure of SFTI-1. We therefore extracted SFTI-1 from sunflower seeds without a trypsin purification step and confirmed that the backbone of SFTI-1 is indeed naturally cyclic. Structural studies on SFTI-1[6,5] revealed high heterogeneity, and multiple species of SFTI-1[6,5] were identified. The main species closely resembles the structure of cyclic SFTI-1 with the broken binding loop able to rotate between a cis/trans geometry of the I7-P8 bond with the cis conformer being similar to the canonical binding loop conformation. The non-reactive loop adopts a beta-hairpin structure as in cyclic wild-type SFTI-1. Another species exhibits an iso-aspartate residue at position 14 and provides implications for possible in vivo cyclization mechanisms.

  • Organizational Affiliation

    Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia.


Find similar proteins by:  Sequence   |   3D Structure  

Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
CYCLIC TRYPSIN INHIBITOR14Helianthus annuusMutation(s): 0 
Membrane Entity: Yes 
Find proteins for Q4GWU5 (Helianthus annuus)
Explore Q4GWU5 
Go to UniProtKB:  Q4GWU5
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ4GWU5
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: SOLUTION NMR
  • Conformers Calculated: 50 
  • Conformers Submitted: 20 
  • Selection Criteria: LEAST OVERALL ENERGIES 

Structure Validation

View Full Validation Report

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2003-03-13
    Type: Initial release
  • Version 1.1: 2011-05-08
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance