Bicyclic peptides: Solid state conformation of cyclo(Glu-Leu-Pro-Gly-Lys-Leu-Pro-Gly)cyclo(1γ-5ϵ)Gly

✍ Scribed by Benedetto Di Blasio; Ettore Benedetti; Vincenzo Pavone; Carlo Pedone; Michele Saviano; Giancarlo Zanotti; Elkan R. Blout

• Publisher: Wiley (John Wiley & Sons)
• Year: 1990
• Tongue: English
• Weight: 547 KB
• Volume: 30
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360300504

✦ Synopsis

The solid state conformational analysis of the ionophoric homodetic bicyclic cyclo ( Glu-Leu-Pro-Gly-Lys-Leu-Pro-G1y)cyclo ( ly-5c) Gly (BCP3) has been carried out by x-ray diffraction. It crystallizes with 4.5 molecules of water per peptide molecule in the monoclinic system, space group PZ1 with a = 11.425 A, b = 16.616 A, c = 13.931 A, /3 = 109.24', and 2 = 2. The structure has been determined by direct methods and refined to an R factor of 0.061 for 2448 observed reflections. The structure characterized by all trans peptide bonds is stabilized by three intramolecular hydrogen bonds: a type I1 P-turn, a mixed type I-type I11 @-turn, and a pseudo y-turn, which involves the side chain C=O and the main-chain N-H groups of the Glu' residue. The resulting globular molecule presents a rather hydrophilic surface with most of the C = O groups available to hydration of the solvent molecules, which are linked through hydrogen bonds of the N-H . . . 0 or 0 -H . . . 0 types in a complicated H-bonding scheme. The conformation observed in the solid state is rather different from the conformation proposed in solution for both the free and the Ca2+-complexed BCP3 molecule.