Context-dependent conformation of diethylglycine residues in peptides

• Published in: The journal of peptide research 2000-04, Vol.55 (4), p.271-278
• Main Authors: Kaul, R., Balaram, P., Banumathi, S., Velmurugan, D., Ravikumar, K., Balaji Rao, R.
• Format: Article
• Language: English
• Subjects: Amino Acid Motifs; Aminobutyrates; Aminoisobutyric Acids - chemistry; Chromatography, High Pressure Liquid; Circular Dichroism; Crystallography, X-Ray; diethylglycine residues; extended C5 conformations; Hydrogen Bonding; Magnetic Resonance Spectroscopy; Models, Molecular; NMR of peptides; peptide conformation; peptide crystal structure; Peptides - chemical synthesis; Peptides - chemistry; Protein Conformation
• ISSN: 1397-002X; 1399-3011
• DOI: 10.1034/j.1399-3011.2000.00150.x

: 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 β‐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) β‐turn.