title: Polypeptide helices in hybrid peptide sequences.
abstract: A new class of polypeptide helices in hybrid sequences containing alpha-, beta-, and gamma-residues is described. The molecular conformations in crystals determined for the synthetic peptides Boc-Leu-Phe-Val-Aib-betaPhe-Leu-Phe-Val-OMe 1 (betaPhe: (S)-beta3-homophenylalanine) and Boc-Aib-Gpn-Aib-Gpn-OMe 2(Gpn: 1-(aminomethyl)cyclohexaneacetic acid) reveal expanded helical turns in the hybrid sequences (alpha alphabeta)n and (alphagamma)n. In 1, a repetitive helical structure composed of C14 hydrogen-bonded units is observed, whereas 2 provides an example of a repetitive C12 hydrogen-bonded structure. Using experimentally determined backbone torsion angles for the hydrogen-bonded units formed by hybrid sequences, we have generated energetically favorable hybrid helices. Conformational parameters are provided for C11, C12, C13, C14, and C15 helices in hybrid sequences.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India.
authors.forename: Kuppanna
authors.initials: K
authors.lastname: Ananda
authors.forename: Prema G
authors.initials: PG
authors.lastname: Vasudev
authors.forename: Anindita
authors.initials: A
authors.lastname: Sengupta
authors.forename: K Muruga Poopathi
authors.initials: KM
authors.lastname: Raja
authors.forename: Narayanaswamy
authors.initials: N
authors.lastname: Shamala
authors.forename: Padmanabhan
authors.initials: P
authors.lastname: Balaram
mesh_terms: D003198:Computer Simulation; D018257:Helix-Loop-Helix Motifs; D006860:Hydrogen Bonding; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary / Q000235:genetics
chemical_list: D010455:Peptides