Abstract
The giant muscle protein titin, also called connectin, is responsible for the elasticity of relaxed striated muscle, as well as acting as the molecular scaffold for thick-filament formation1,2. The titin molecule consists largely of tandem domains of the immuno-globulin and fibronectin-III types, together with specialized binding regions and a putative elastic region, the PEVK domain3. We have done mechanical experiments on single molecules of titin to determine their visco-elastic properties, using an optical-tweezers technique. On a fast (0.ls) timescale titin is elastic and force–extension data can be fitted with standard random-coil polymer models, showing that there are two main sources of elasticity: one deriving from the entropy of straightening the molecule; the other consistent with extension of the polypeptide chain in the PEVK region. On a slower timescale and above a certain force threshold, the molecule displays stress-relaxation, which occurs in rapid steps of a few piconewtons, corresponding to yielding of internal structures by about 20 nm. This stress-relaxation probably derives from unfolding of immu-noglobulin and fibronectin domains.
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Tskhovrebova, L., Trinick, J., Sleep, J. et al. Elasticity and unfolding of single molecules of the giant muscle protein titin. Nature 387, 308–312 (1997). https://doi.org/10.1038/387308a0
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DOI: https://doi.org/10.1038/387308a0
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