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Two peptide fragments G55–I72 and K97–A109 from staphylococcal nuclease exhibit different behaviors in conformational preferences for helix formation
Author(s) -
Wang Min,
Shan Lu,
Wang Jinfeng
Publication year - 2006
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.20558
Subject(s) - chemistry , crystallography , circular dichroism , helix (gastropod) , micrococcal nuclease , folding (dsp implementation) , protein folding , random coil , protein structure , peptide , stereochemistry , biochemistry , dna , ecology , nucleosome , snail , electrical engineering , histone , biology , engineering
Abstract Two synthetic peptides, SNaseα1 and SNaseα2, corresponding to residues G55–I72 and K97–A109, respectively, of staphylococcal nuclease (SNase), are adopted for detecting the role of helix α1 (E57–A69) and helix α2 (M98–Q106) in the initiation of folding of SNase. The helix‐forming tendencies of the two SNase peptide fragments are investigated using circular dichroism (CD) and two‐dimensional (2D) nuclear magnetic resonance (NMR) methods in water and 40% trifluoroethanol (TFE) solutions. The coil–helix conformational transitions of the two peptides in the TFE–H 2 O mixture are different from each other. SNaseα1 adopts a low population of localized helical conformation in water, and shows a gradual transition to helical conformation with increasing concentrations of TFE. SNaseα2 is essentially unstructured in water, but undergoes a cooperative transition to a predominantly helical conformation at high TFE concentrations. Using the NMR data obtained in the presence of 40% TFE, an ensemble of α‐helical structures has been calculated for both peptides in the absence of tertiary interactions. Analysis of all the experimental data available indicates that formation of ordered α‐helical structures in the segments E57–A69 and M98–Q106 of SNase may require nonlocal interactions through transient contact with hydrophobic residues in other parts of the protein to stabilize the helical conformations in the folding. The folding of helix α1 is supposed to be effective in initiating protein folding. The formation of helix α2 depends strongly on the hydrophobic environment created in the protein folding, and is more important in the stabilization of the tertiary conformation of SNase. © 2006 Wiley Periodicals, Inc. Biopolymers 83:268–279, 2006 This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com