title: Conformation of di-n-propylglycine residues (Dpg) in peptides: crystal structures of a type I' beta-turn forming tetrapeptide and an alpha-helical tetradecapeptide.
abstract: The crystal structures of two oligopeptides containing di-n-propylglycine (Dpg) residues, Boc-Gly-Dpg-Gly-Leu-OMe (1) and Boc-Val-Ala-Leu-Dpg-Val-Ala-Leu-Val-Ala-Leu-Dpg-Val-Ala-Leu-OMe (2) are presented. Peptide 1 adopts a type I'beta-turn conformation with Dpg(2)-Gly(3) at the corner positions. The 14-residue peptide 2 crystallizes with two molecules in the asymmetric unit, both of which adopt alpha-helical conformations stabilized by 11 successive 5 --> 1 hydrogen bonds. In addition, a single 4 --> 1 hydrogen bond is also observed at the N-terminus. All five Dpg residues adopt backbone torsion angles (phi, psi) in the helical region of conformational space. Evaluation of the available structural data on Dpg peptides confirm the correlation between backbone bond angle N-C(alpha)-C' (tau) and the observed backbone phi,psi values. For tau > 106 degrees, helices are observed, while fully extended structures are characterized by tau < 106 degrees. The mean tau values for extended and folded conformations for the Dpg residue are 103.6 degrees +/- 1.7 degrees and 109.9 degrees +/- 2.6 degrees, respectively.
authors: Department of Physics, Indian Institute of Science, Bangalore, India.
authors: Raghurama P
authors: RP
authors: Hegde
authors: Subrayashastry
authors: S
authors: Aravinda
authors: Rajkishor
authors: R
authors: Rai
authors: Ramesh
authors: R
authors: Kaul
authors: Sarojini
authors: S
authors: Vijayalakshmi
authors: R Balaji
authors: RB
authors: Rao
authors: Narayanaswamy
authors: N
authors: Shamala
authors: Padmanabhan
authors: P
authors: Balaram
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D014633:Valine / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: D046912:Multiprotein Complexes; D009842:Oligopeptides; D010455:Peptides; C038263:dipropylglycine; D014633:Valine