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Solution conformations of peptides representing the sequence of the toxin pardaxin and analogues in trifluoroethanol‐water mixtures: Analysis of CD spectra
Author(s) -
Thennarasu Sathiah,
Nagaraj Ramakrishnan
Publication year - 1997
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/(sici)1097-0282(199705)41:6<635::aid-bip4>3.0.co;2-r
Subject(s) - chemistry , peptide , polyproline helix , circular dichroism , aqueous solution , stereochemistry , residue (chemistry) , protein secondary structure , alanine , amino acid , biochemistry , organic chemistry
The cytolytic activities and conformational properties of pardaxin (GFFALIPKIISSPLFKTLLSAVGSALSSSGEQE), a 33‐residue linear peptide that exhibits unusual shark repellent and cytolytic activities, and its analogues have been examined in aqueous environment and trifluoroethanol (TFE) using CD spectroscopy. A peptide corresponding to the 1–26 segment and an analogue where P7 has been changed to A show greater hemolytic activity than pardaxin. While the peptide corresponding to the N‐terminal 18‐residue segment does not exhibit hemolytic activity, its analogue where P7 is replaced by A is hemolytic. The secondary structural propensities of the peptides were inferred by deconvolution of the experimental spectra into pure components. Pardaxin, its variant where proline at position 7 was replaced by alanine, and shorter peptides corresponding to N‐terminal segments exist in multiple conformations in aqueous medium that are comprised of β‐turn, β‐sheet, and distorted helical structures. With increasing proportions of TFE, while helical conformation predominates in all the peptides, both distorted and the regular α‐helices appear to be populated. Analysis of CD spectra by deconvolution methods appears to be a powerful tool for delineating multiple conformations in peptides, especially membrane‐active peptides that encounter media of different polarity ranging from aqueous environment to one of low dielectric constant in the hydrophobic interior of membranes. Our study provides further insights into the structural requirements for the biological activity of pardaxin and related peptides. © 1997 John Wiley & Sons, Inc. Biopoly 41: 635–645, 1997