title: Conformational studies of [Abu(3, 11)]-SFTI-1, an analogue of the trypsin inhibitor isolated from sunflower seeds.
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.
authors: Faculty of Chemistry, University of Gdańsk, Sobieskiego 18, PL-80-952 Gdańsk, Poland.
authors: Krzysztof
authors: K
authors: Brzozowski
authors: Radosław
authors: R
authors: Majewski
authors: Anna
authors: A
authors: Jaśkiewicz
authors: Anna
authors: A
authors: Legowska
authors: Lidia
authors: L
authors: Klaudel
authors: Sylwia
authors: S
authors: Rodziewicz-Motowidło
authors: Krzysztof
authors: K
authors: Rolka
mesh_terms: D000465:Algorithms; D000613:Aminobutyrates / Q000737:chemistry*; D003198:Computer Simulation; D006368:Helianthus / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008956:Models, Chemical; D008958:Models, Molecular; D008970:Molecular Weight; D010456:Peptides, Cyclic / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D011487:Protein Conformation; D012639:Seeds / Q000737:chemistry*; D014357:Trypsin / Q000187:drug effects; D014361:Trypsin Inhibitors / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D000613:Aminobutyrates; D010456:Peptides, Cyclic; C448501:SFTI-1 peptide, sunflower; D014361:Trypsin Inhibitors; C012223:alpha-aminobutyric acid; D014357:Trypsin