Case Study: Titin Ig domains

In the extreme sport of bungee jumping, a daring athlete leaps from a great height and freefalls while a tethered cord tightens and stretches to absorb the energy from the descent. The bungee cord protects the jumper from serious injury, because its elasticity allows it to extend and provide a cushioning force that opposes gravity during the fall. Amazingly, nature also uses elasticity to dampen biological forces at the molecular level, such as during extension of a muscle fiber under stress. The molecular bungee cord that serves this purpose in the human muscle fiber is the protein titin, which functions to protect muscle fibers from damage due to overstretching. In this case study, we will examine how experimental and theoretical studies yield insight into the molecular mechanism for titin’s elasticity.