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Single‐residue substitution in homopolypeptides: Perturbative helix–coil theory at a single site
Author(s) -
Qian Hong
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.360331010
Subject(s) - chemistry , substitution (logic) , helix (gastropod) , peptide , helicity , residue (chemistry) , electromagnetic coil , alpha helix , amino acid substitution , crystallography , stereochemistry , circular dichroism , physics , organic chemistry , quantum mechanics , ecology , biochemistry , snail , computer science , mutant , gene , biology , programming language
Abstract Based on Lifson–Roig's helix–coil transition theory, substitution of a single heteroresidue into a homopolymer host is studied. This study models recent experiments that substitute a single amino acid into a small peptide in water [A. Chakrabartty, J. A. Schellman, and R. L. Baldwin (1991), Nature , Vol. 351, pp. 586–688]. Our formalism, which is based on a perturbation method, differs from the existing theory for sequenced polymers and is naturally analogous, hence likely to be useful, to substitution experiments in the laboratory. It is shown that the intrinsic helix propensity w is directly proportional to the equilibrium constant for the helix–coil equilibrium of a single residue in a host peptide. This intuitive new result will simplify experimental data interpretations for measurements of the helical conformation on the single amino acid level. It is also shown that substitution affects the total helicity of the host peptide according to two considerations: the helicity of the replaced residue prior to the substitution, and the sensitivity of the site, a measure of neighboring interactions. The relationship between substitution stability and thermal stability is explored. © 1993 John Wiley & Sons, Inc.