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‐Gin‐Gly‐Ile‐NMA from the β‐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 α‐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 3‐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.