title: Context-dependent conformation of diethylglycine residues in peptides.
abstract: Diethylglycine (Deg) residues incorporated into peptides can stabilize fully extended (C5) or helical conformations. The conformations of three tetrapeptides Boc-Xxx-Deg-Xxx-Deg-OMe (Xxx=Gly, GD4; Leu, LD4 and Pro, PD4) have been investigated by NMR. In the Gly and Leu peptides, NOE data suggest that the local conformations at the Deg residues are fully extended. Low temperature coefficients for the Deg(2) and Deg(4) NH groups are consistent with their inaccessibility to solvent, in a C5 conformation. NMR evidence supports a folded beta-turn conformation involving Deg(2)-Gly(3), stabilized by a 4-->1 intramolecular hydrogen bond between Pro(1) CO and Deg(4) NH in the proline containing peptide (PD4). The crystal structure of GD4 reveals a hydrated multiple turn conformation with Gly(1)-Deg(2) adopting a distorted type II/II' conformation, while the Deg(2)-Pro(3) segment adopts a type III/III' structure. A lone water molecule is inserted into the potential 4-->1 hydrogen bond of the Gly(1)-Deg(2) beta-turn.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore.
authors.forename: R
authors.initials: R
authors.lastname: Kaul
authors.forename: S
authors.initials: S
authors.lastname: Banumathi
authors.forename: D
authors.initials: D
authors.lastname: Velmurugan
authors.forename: K
authors.initials: K
authors.lastname: Ravikumar
authors.forename: R
authors.initials: R
authors.lastname: Balaji Rao
authors.forename: P
authors.initials: P
authors.lastname: Balaram
mesh_terms: D020816:Amino Acid Motifs; D000613:Aminobutyrates; D000621:Aminoisobutyric Acids / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011487:Protein Conformation
chemical_list: D000613:Aminobutyrates; D000621:Aminoisobutyric Acids; D010455:Peptides; C062694:alpha-amino-2-ethylbutanoic acid