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Elasticity of the Transition State Leading to an Unexpected Mechanical Stabilization of Titin Immunoglobulin Domains
Author(s) -
Yuan Guohua,
Le Shimin,
Yao Mingxi,
Qian Hui,
Zhou Xin,
Yan Jie,
Chen Hu
Publication year - 2017
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201700411
Subject(s) - titin , immunoglobulin domain , sarcomere , magnetic tweezers , elasticity (physics) , chemistry , biophysics , optical tweezers , physics , thermodynamics , biology , biochemistry , microbiology and biotechnology , myocyte , receptor , quantum mechanics
The giant protein titin plays a critical role in regulating the passive elasticity of muscles, mainly through the stochastic unfolding and refolding of its numerous immunoglobulin domains in the I‐band of sarcomeres. The unfolding dynamics of titin immunoglobulin domains at a force range greater than 100 pN has been studied by atomic force microscopy, while that at smaller physiological forces has not been measured before. By using magnetic tweezers, it is found that the titin I27 domain unfolds in a surprising non‐monotonic force‐dependent manner at forces smaller than 100 pN, with the slowest unfolding rate occurring around 22 pN. We further demonstrate that a model with single unfolding pathway taking into account the elasticity of the transition state can reproduce the experimental results. These results provide important novel insights into the regulation mechanism of the passive elasticity of muscle tissues.