Titin immunoglobulin domain refolding produces mechanical work in situ

Titin's proximal immunoglobulin domains have been shown to unfold and refold at physiological forces in isolated protein constructs. In this study, we use mechanical testing of intact isolated rabbit psoas myofibrils coupled with mathematical modeling to confirm that immunoglobulin domain unfolding and refolding does indeed occur at physiological forces in situ. We show that immunoglobulin domains refold at physiological forces, when titin is situated in its physiological configuration in an intact sarcomere.