ABSTRACT
The conformational space of six tetrapeptides from the beta-bends in the third loop of short-chain snake venom neurotoxins was investigated with the aid of energy calculations. It was shown that these peptides can be divided into two groups: those with a specific preference for an alpha-helix and those that exist as an ensemble of beta-turn conformations.
Subject(s)
Neurotoxins/chemistry , Snake Venoms/chemistry , Amino Acid Sequence , Animals , Molecular Sequence Data , Peptides/chemistry , Protein Conformation , ThermodynamicsABSTRACT
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.
Subject(s)
Neurotoxins/chemistry , Oligopeptides/chemistry , Snake Venoms/chemistry , Amino Acid Sequence , Circular Dichroism , Magnetic Resonance Spectroscopy , Molecular Sequence Data , Protein Conformation , Protein Structure, Secondary , ThermodynamicsABSTRACT
The conformational space of the tetrapeptide Ac-Lys-Pro-Gly-Ile-NMA from the beta-bend present in the third loop of short-chain snake venom neurotoxins was investigated with the aid of energy calculations, resulting in the identification of an ensemble of beta-turn conformations. These results were compared with the experimentally determined conformations, as observed using NMR and CD spectroscopy. A random coil conformation of the peptide is indicated in polar hydrogen-bonding solvents. In less polar solvents the peptide backbone assumed a more rigid conformation, as reflected by the existence of at least a type II beta-turn conformation.
