LARGE ROD-LIKE FORCE-BEARING PROTEINS AS MOLECULAR SHOCK ABSORBERS
Mechanobiology Institute, National University of Singapore, Singapore; National University of Singapore, Singapore
Large force-bearing proteins that are comprised of a linear array of modular domains are often found as mechanical linkages at adhesion sites of a cell to its extracellular environment and to its neighboring cells. These proteins are subject to frequent stretch and relaxation during actomyosin contraction and relaxation. We show that such proteins can act as a force buffer, keeping the force in the force-transmission pathways they mediate within certain range depending on the mechanical stability of their internal domains. This force-buffering function is a result from a simple physical principle: increased tension during stretching of a protein drives unfolding of its internal domains, preventing tension accumulation. In contrast, during mechanical relaxation, the reduced tension drives refolding of the domains, preventing tension from dropping too fast. We demonstarte the principle using talin in cell-ECM focal adhesion sites and titin in sarcomere of muscles as examples. A tightly controlled tension range by such force-buffering proteins has an apparent advantage of allowing robust mechanosensitive interactions to take place.