Folding-unfolding transitions in single titin molecules characterized with laser tweezers

Miklós S Z Kellermayer, Steven B. Smith, Hendrikus "Henk" Granzier, Carlos Bustamante

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Abstract

Titin, a giant filamentous polypeptide, is believed to play a fundamental role in maintaining sarcomeric structural integrity and developing what is known as passive force in muscle. Measurements of the force required to stretch a single molecule revealed that titin behaves as a highly nonlinear entropic spring. The molecule unfolds in a high-force transition beginning at 20 to 30 piconewtons and refolds in a low-force transition at ~2.5 piconewtons. A fraction of the molecule (5 to 40 percent) remains permanently unfolded, behaving as a wormlike chain with a persistence length (a measure of the chain's bending rigidity) of 20 angstroms. Force hysteresis arises from a difference between the unfolding and refolding kinetics of the molecule relative to the stretch and release rates in the experiments, respectively. Scaling the molecular data up to sarcomeric dimensions reproduced many features of the passive force versus extension curve of muscle fibers.

Original languageEnglish (US)
Pages (from-to)1112-1116
Number of pages5
JournalScience
Volume276
Issue number5315
DOIs
Publication statusPublished - May 16 1997
Externally publishedYes

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