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Conformational studies of [Abu 3, 11 ]‐SFTI‐1, an analogue of the trypsin inhibitor isolated from sunflower seeds
Author(s) -
Brzozowski Krzysztof,
Majewski Radosław,
Jaśkiewicz Anna,
Łȩgowska Anna,
Klaudel Lidia,
RodziewiczMotowidło Sylwia,
Rolka Krzysztof
Publication year - 2008
Publication title -
journal of peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 66
eISSN - 1099-1387
pISSN - 1075-2617
DOI - 10.1002/psc.1025
Subject(s) - chemistry , cyclic peptide , peptide , stereochemistry , conformational isomerism , disulfide bond , trypsin , nuclear magnetic resonance spectroscopy , trypsin inhibitor , molecular dynamics , molecule , computational chemistry , biochemistry , enzyme , organic chemistry
Abstract With only 14 amino acid residues, the trypsin inhibitor SFTI‐1 is the smallest naturally occurring serine proteinase inhibitor. It consists of two cyclic fragments (with head‐to‐tail cyclization and a disulfide bridge). In our previous paper, we showed that the removal of the disulfide bridge produced 2.4‐fold lower activity. Here, we present the total conformational analysis of the [Abu 3, 11 ]‐SFTI‐1 analog by means of 2D NMR spectroscopy in conjunction with theoretical methods. The peptide was synthesized by Fmoc SPPS. It was cyclized with PyBop and DIPEA in DMF. The NMR studies were performed in DMSO‐ d 6 at 303 K. Conformations of the peptide studied were calculated by the following three approaches: distance geometry (DG), molecular dynamics (MD) and determination of the statistical weights of conformations. The first two algorithms use a CHARMM force field, whereas the last uses an ECEPP/3 force field. Our calculations resulted in three sets of conformers with 7, 9 and 6 representatives, respectively. All our results were compared with published ones. It was found that the peptide has an ill‐defined structure. Despite its conformational flexibility, the binding loop (3–11 fragment) displayed geometry similar to the corresponding fragments of the other SFTI‐1 analogs and to the inhibitor itself. Furthermore, the peptide bond between the Ile7 and Pro8 residues adopts cis geometry, which is essential for inhibitory activity. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.