Structure of cyclic peptides: the crystal and solution conformation of cyclo(Phe-Phe-Aib-Leu-Pro)(1092 views) Zanotti G, Saviano M, Saviano G, Tancredi T, Rossi F, Pedone C, Benedetti E
Journal Of Peptide Research (ISSN: 1397-002x), 1998 Jun; 51(6): 460-466.
Keywords: Cambridge Crystallographic Database, Cyclic Pentapeptides, X-Ray Diffraction, Cyclopeptide, Article, Crystal Structure, Hydrogen Bond, Nuclear Magnetic Resonance Spectroscopy, Priority Journal, Protein Binding, Protein Conformation, Protein Structure, X Ray Diffraction, Models, Molecular, Solutions,
Affiliations: Ctro. Stud. sulla Chim. F., C.N.R, Univ. di Roma La Sapienza, Piazzale A. Moro 5, 00185 Roma, Italy
Ctro. Stud. Biocristallografia, Dipartimento di Chimica, Univ. Studi di Napoli Federico II, via Mezzocannone 4, 80134 Napoli, Italy
Ist. per Chim. Molecole Interesse B., C.N.R., via Toiano 6, I-80072 Arco Felice, Italy
References: Not available.
Structure of cyclic peptides: the crystal and solution conformation of cyclo(Phe-Phe-Aib-Leu-Pro)
A solid-state and solution conformation analyses of the cyclopentapeptide cyclo(Phe-Phe-Aib-Leu-Pro) has been carried out by X-ray diffraction and nuclear magnetic resonance techniques. The structure of the hexagonal crystals, grown from a methanol solution [a = b = 16.530(4) Angstrom, c = 21.356(9) Angstrom, space group P6(5), Z = 6], shows the presence of one intramolecular N-H ... O=C hydrogen bond with the formation of a gamma-turn (C-7). The Aib(3) residue, at the center of the gamma-turn, presents unexpected values of the torsion angles [phi = 70.5 degrees and psi = -73.8 degrees], which have been observed only once before for this helicogenic residue. A cis peptide bond occurs between Leu(4) and Pro(5); all other peptide bonds are trans. The overall conformation for the cyclopentapeptide with one cis-peptide bond on one side and an intramolecular gamma-turn on the opposite side results in an equatorial topology of the side-chains of the Phe(1), Phe(2) and Leu(4) residues. Indeed, the C-alpha-C-beta and C-beta-C-gamma bonds of these residues lie approximately in the mean plane of the cyclic ring system. The structure is compared with data in the literature on cyclic pentapeptides. In addition the Pro-Phe-Phe moiety shows a conformation similar to that observed in other larger cyclic bioactive peptides, which indicates a reduced number of conformations for this sequence. The solution study was carried out in three different solvent systems chloroform, acetonitrile and methanol in the temperature interval 220-300 K, In all three solvents the room temperature spectra show that the peptide is conformationally nonhomogeneous. In acetonitrile at low temperatures it is possible to reduce the conformational equilibrium to two predominant conformers which differ for the cis-trans isomerism of the Leu(4)-Pro(5) peptide bond. (C) Munksgaard 1998.
Structure of cyclic peptides: the crystal and solution conformation of cyclo(Phe-Phe-Aib-Leu-Pro)