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Entropy Drives the Formation of Salt Bridges in the Protein GB3
Author(s) -
Zhang Ning,
Wang Yefei,
An Liaoyuan,
Song Xiangfei,
Huang Qingshan,
Liu Zhijun,
Yao Lishan
Publication year - 2017
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201702968
Subject(s) - salt bridge , chemistry , salt (chemistry) , solvent , entropy (arrow of time) , conformational entropy , molecular dynamics , titration , thermodynamics , crystallography , molecule , computational chemistry , organic chemistry , biochemistry , mutant , physics , gene
Salt bridges are very common in proteins. But what drives the formation of protein salt bridges is not clear. In this work, we determined the strength of four salt bridges in the protein GB3 by measuring the Δp K a values of the basic residues that constitute the salt bridges with a highly accurate NMR titration method at different temperatures. The results show that the Δp K a values increase with temperature, thus indicating that the salt bridges are stronger at higher temperatures. Fitting of Δp K a values to the van't Hoff equation yields positive Δ H and Δ S values, thus indicating that entropy drives salt‐bridge formation. Molecular dynamics simulations show that the protein and solvent make opposite contributions to Δ H and Δ S . Specifically, the enthalpic gain contributed from the protein is more than offset by the enthalpic loss contributed from the solvent, whereas the entropic gain originates from the desolvation effect.