TITIN, A HUGE, ELASTIC SARCOMERIC PROTEIN WITH A PROBABLE ROLE IN MORPHOGENESIS

Titin, the largest protein identified to date (over 1-mu-m long, almost 3 million daltons in mass) is the third most abundant component of the sarcomere. In the mature myofibril, titin molecules span from M line to Z line, forming a third filament system which provides sarcomeric alignment and elastic recoil. In the developing sarcomere, accumulating evidence from studies both in vivo and in vitro implicates titin as part of a morphogenetic scaffolding, upon which critical events in myofibrillogenesis are coordinated in a time- and space-dependent manner.