title: Experimental studies and potential-energy calculations of the blocked tetrapeptide Ac-Lys-Gln-Gly-Ile-NMA from the third loop of a short-chain snake venom neurotoxin.
abstract: The conformational space of the tetrapeptide Ac-Lys-Gln-Gly-Ile-NMA from the beta-bend in the third loop of a short-chain snake venom neurotoxin was investigated with the aid of energy calculations. It was shown that this peptide has a preference for an alpha-helical conformation. This result was compared with the experimentally determined conformations, as observed using NMR and CD spectroscopy. With NMR spectroscopy a random-coil conformation of the peptide is indicated in H2O, DMSO and TFE. The results from the CD experiments suggest that the peptide exists as a random coil in water, but a small population of alpha-helical conformations is present in TFE. These results indicate that additional long-range interactions also play a role in the conformation of this tetrapeptide in the protein.
authors.affiliation: Department of Chemistry, University of Pretoria, South Africa.
authors.forename: H M
authors.initials: HM
authors.lastname: Roos
authors.forename: P H
authors.initials: PH
authors.lastname: Van Rooyen
authors.forename: P L
authors.initials: PL
authors.lastname: Wessels
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009498:Neurotoxins / Q000737:chemistry*; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012910:Snake Venoms / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D009498:Neurotoxins; D009842:Oligopeptides; D012910:Snake Venoms