Infographic: Triggering Titin

This third filament involved in muscle function is often ignored in medical textbooks. Here's how it works.

Sep 1, 2018
Julio M. Fernández

MUSCULAR DOGMA

The standard textbook model of muscle contraction includes only two main players, the filaments actin and myosin, which slide past each other, causing the sarcomere—the basic unit of muscle tissue—to shorten. Driven by ATP-powered myosin motors, sarcomere contraction causes whole muscles to shorten. In the past 40 years, researchers have explored the role of another filament: titin. Its emerging role in muscle function, unwinding during muscle relaxation and folding during contraction, suggests that the ATP-driven motors also act as latches allowing titin to fold, providing a powerful boost to muscle contraction.

© IKUMI KAYAMA/STUDIO KAYAMA

Relaxed

When sarcomeres are relaxed titin, anchored to teh Z line and the ends of myosin filaments, unwinds.
© IKUMI KAYAMA/STUDIO KAYAMA

Contracted

When sarcomeres contract, titin folds again, adding force to the contraction.
© ikumi kayama/studio kayama


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