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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