title: The turn sequence directs beta-strand alignment in designed beta-hairpins.
abstract: A previous NMR investigation of model decapeptides with identical beta-strand sequences and different turn sequences demonstrated that, in these peptide systems, the turn residues played a more predominant role in defining the type of beta-hairpin adopted than cross-strand side-chain interactions. This result needed to be tested in longer beta-hairpin forming peptides, containing more potentially stabilizing cross-strand hydrogen bonds and side-chain interactions that might counterbalance the influence of the turn sequence. In that direction, we report here on the design and 1H NMR conformational study of three beta-hairpin forming pentadecapeptides. The design consists of adding two and three residues at the N- and C-termini, respectively, of the previously studied decapeptides. One of the designed pentadecapeptides includes a potentially stabilizing R-E salt bridge to investigate the influence of this interaction on beta-hairpin stability. We suggest that this peptide self-associates by forming intermolecular salt bridges. The other two pentadecapeptides behave as monomers. A conformational analysis of their 1H NMR spectra reveals that they adopt different types of beta-hairpin structure despite having identical strand sequences. Hence, the beta-turn sequence drives beta-hairpin formation in the investigated pentadecapeptides that adopt beta-hairpins that are longer than the average protein beta-hairpins. These results reinforce our previous suggestion concerning the key role played by the turn sequence in directing the kind of beta-hairpin formed by designed peptides.
authors.affiliation: Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas, Madrid, Spain.
authors.forename: E
authors.initials: E
authors.lastname: de Alba
authors.forename: M
authors.initials: M
authors.lastname: Rico
authors.forename: M A
authors.initials: MA
authors.lastname: Jiménez
mesh_terms: D000595:Amino Acid Sequence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: D009842:Oligopeptides; D010455:Peptides