title: Coexistence of folded and extended conformations of a tripeptide containing alpha, alpha -di-n-propylglycine in crystals.
abstract: The crystal structure of the tripeptide Boc-Leu-Dpg-Val-OMe (Dpg, alpha, alpha -di-n-propylglycine) reveals the coexistence of two distinct backbone conformations. In molecule A the Dpg residue adopts a fully extended conformation (phi = 76.0 degrees, psi = 180.0 degrees) while in molecule B a left handed helical conformation (phi = 62.8 degrees, psi = 39.6 degrees) is observed. Molecule B adopts a folded structure corresponding to a highly distorted Type II beta-turn conformation, which lacks an intramolecular 4 -> 1 hydrogen bond. In contrast, molecule A has an open, extended conformation. The results demonstrate that both fully extended and helical conformations are energetically accessible to the Dpg residue.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore.
authors.forename: S
authors.initials: S
authors.lastname: Prasad
authors.forename: S
authors.initials: S
authors.lastname: Mitra
authors.forename: E
authors.initials: E
authors.lastname: Subramanian
authors.forename: D
authors.initials: D
authors.lastname: Velmurugan
authors.forename: R B
authors.initials: RB
authors.lastname: Rao
authors.forename: P
authors.initials: P
authors.lastname: Balaram
mesh_terms: D008958:Models, Molecular; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation; D014633:Valine / Q000031:analogs & derivatives* / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D009842:Oligopeptides; C085553:t-butyloxycarbonyl-leucyl-dipropylglycyl-valine methyl ester; C038263:dipropylglycine; D014633:Valine