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Permethylation alters the conformational transitions and the complexing ability of melittin: A model for methylated proteins
Author(s) -
Ramalingam Kalaiyarasi,
Bello Jake,
Aimoto Saburo
Publication year - 1993
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/bip.360330212
Subject(s) - melittin , chemistry , random coil , tetramer , crystallography , glycine , peptide , stereochemistry , amino acid , circular dichroism , biochemistry , enzyme
Melittin exhibits a transition from random‐coil monomer to helical tetramer as a function of peptide concentration [ J. Bello, H. R. Bello, and E. Granados (1982) Biochemistry , Vol. 21, pp. 461–465]. When permethylated on each of the four amino groups (Gly‐1 Nα and Lys‐7, 21, and 23 Nε) to yield trimethylammonium groups, melittin exists as a random coil and does not show any concentration‐dependent conformational transition (up to 290 μ M ). Acylation of the amino groups of melittin with glycine or 5‐aminopentanoic acid followed by permethylation increases helix formation, but to a lesser extent than for the unmethylated aminoacylmelittin derivatives. The results are discussed in relation to hydrophobicity, charge repulsions, and ion binding. Melittin, and more weakly, permethylated melittin (MLT‐Me) form helical hybrids with an anionic random‐coil melittin analogue (E‐MLT), in which all the lysine and arginine residues of melittin were replaced by glutamate residues. The hybrid between MLT‐Me and E‐MLT shows a concentration‐dependent increase in helicity. E‐MLT, when succinylated at the N‐terminal glycine (E‐MLT‐suc), forms a stronger hybrid with MLT‐Me, possibly as a result of increased electrostatic interaction between equal but opposite charges in E‐MLT‐suc (net charge –6) and MLT‐Me (net charge +6). The hybrids exhibit both cold‐ and heat‐induced denaturation, similar to the phenomenon exhibited by proteins. The hybrids also exhibit significant residual structures in the temperature range of 80–100°C, which may be similar to the molten globular states that have been suggested for proteins. © 1993 John Wiley & Sons, Inc.