Interactions responsible for the pH dependence of the beta-hairpin conformational population formed by a designed linear peptide.
In a previous work [Blanco, F.J., Jiménez, M.A., Herranz, J., Rico, M., Santoro, J. & Nieto, J. L. (1993) J. Am. Chem. Soc. 115, 5887-5888] we showed that a short, designed linear peptide, YQNPDGSQA (peptide 1), can form a monomeric beta hairpin in aqueous solution. The pH dependence of the beta-hairpin conformation formed by the designed peptide and a series of related peptides has been examined in this work using 1H-NMR methods. Three pH-dependent interactions have been identified: a local interaction, unimportant structurally, between the C-terminal carboxylate group and the side-chain amide group of Q8; an electrostatic interaction between the main-chain N-terminus and C-terminus; and a hydrogen bond involving the side-chain amide protons of N3 and the side-chain carboxylate group of D5. The latter two interactions are particularly relevant as they increase the population of the beta-hairpin conformation. We also observe in the mutant peptide A9H that the interaction between Y1 and H9 (of the type proposed to exist in proteins) does not contribute to beta-hairpin stabilisation in our peptide system. Peptide 1 is, therefore, a very suitable model to examine the different interactions that contribute to beta-hairpin stability.
de Alba
E
E
Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Blanco
F J
FJ
Jiménez
M A
MA
Rico
M
M
Nieto
J L
JL
D000595:Amino Acid Sequence; D015195:Drug Design; D004355:Drug Stability; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011522:Protons; D013696:Temperature
D009842:Oligopeptides; D011522:Protons