Description |
We do not know why the mechanical stretching of muscle tissues, such as during yoga, is so beneficial for humans. Current theories of muscle contraction propose that the power stroke of a myosin motor is the sole source of mechanical energy driving the sliding filaments of a contracting muscle. Amazingly, these models exclude titin, the largest protein in the human body, which determines the passive elasticity of muscles and is mechanically unfolded by stretching. During my lecture I will provide evidence at the single molecule level, that stepwise unfolding and folding of titin Ig domains occurs in the elastic I band region of intact myofibrils at physiological sarcomere lengths and forces of 6-8 pN. Further, I will show that titin folding does mechanical work at these forces that is up to three times larger than that generated by a myosin motor. Therefore, it appears inescapable that folding of titin Ig domains is an important, but so far unrecognized contributor to the force generated by a contracting muscle. Thus, ancient wisdom was right again: recruiting titin domains to the unfolded state by stretching greatly increases the storage of elastic energy in muscle, which is an essential component of muscle contraction.
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