TCB Publications - Abstract

Eric H. Lee, Jen Hsin, Eleonore von Castelmur, Olga Mayans, and Klaus Schulten. Tertiary and secondary structure elasticity of a six-Ig titin chain. Biophysical Journal, 98:1085-1095, 2010. (PMC: 2849065)

LEE2010 The protein titin functions as a mechanical spring conferring passive elasticity to muscle. Force spectroscopy studies have shown that titin exhibits several regimes of elasticity. Disordered segments bring about a soft, entropic spring-type elasticity; secondary structures of titin’s immunoglobulin-like (Ig-) and fibronectin type III-like (FN-III) domains provide a stiff elasticity. In this study we demonstrate a third type of elasticity due to tertiary structure and involving domain-domain interaction and reorganization along the titin chain. Through altogether 870 ns of molecular dynamics (MD) simulations involving 29,000 – 635,000 atom systems, the mechanical properties of a six-Ig domain of titin (I65-I70), for which a crystallographic structure is available, are probed. The results reveal a soft tertiary structure elasticity. A remarkably accurate statistical mechanical description for this elasticity is derived and applied. Simulations studied also the stiff, secondary structure elasticity of the I65-I70 chain due to the unraveling of its domains and revealed how force propagates along the chain during the secondary structure elasticity response.

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