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Conformational structure of the amphipathic peptide insecticide L‐KALA
Author(s) -
Nandel Fateh S.,
Ahluwalia Anupam,
Kaur Amandeep
Publication year - 1995
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560550109
Subject(s) - chemistry , hydrogen bond , vesicle , amphiphile , helix (gastropod) , peptide , solvation , side chain , intermolecular force , crystallography , residue (chemistry) , aqueous solution , stereochemistry , tetrapeptide , molecule , organic chemistry , membrane , copolymer , ecology , biochemistry , snail , biology , polymer
The conformation structure of the tetrapeptide Ac–Lys–Ala–Leu–Ala–OMe, the repeat unit of a 30 residue peptide YAA(KALA) 6 LAA, and also its analog containing an unusual amino acid, (Aib): Ac–Lys–Aib–Leu–Aib–OMe, has been investigated by the PCILO method. The global/low‐energy minima for all the residues lies at ϕ = −30° and ψ = 120°. In this conformation, the potential hydrogen‐bonding sites are free, i.e., capable of intermolecular hydrogen bonding. As the angles lie closer to the collagen helical region and potential hydrogen‐bonding sites are free, this structure is named the collagen‐type helix. In aqueous solution, this structure is stabilized by solvation of the peptide bond. The local‐energy minimum in all maps correspond to the right‐handed helical region. The helix thus formed generates a pore of 3 Å along the helix axis, with one lateral hydrophobic side and the other hydrophilic side. The pore thus formed is cation‐selective and accounts for the leakage of contents from vesicles. On the basis of the length of the helix and placement of the side chains of lysine and leucine, a model has been proposed for the aggregation and fusion of the vesicles. The amphipathic basic residues interact with the head groups of the acidic liposomes by extending toward the polar face of the helix to insert their charged moieties by overcoming the electrostatic repulsive forces between the opposing vesicles. © 1995 John Wiley & Sons, Inc.