Flightin is necessary for length determination, structural integrity, and large bending stiffness of insect flight muscle thick filaments.

Despite the fundamental role of thick filaments in muscle contraction, little is known about the mechanical behavior of these filaments and how myosin-associated proteins dictate differences between muscle types. In this study, we used atomic force microscopy to study the morphological and mechanical properties of fully hydrated native thick filaments isolated from indirect flight muscle (IFM) of normal and mutant Drosophila lacking flightin (fln(0)). IFM thick filaments from newly eclosed (0-1 h old) wild-type flies have a mean length of 3.

Nanomechanics of native thick filaments from indirect flight muscles.

During flight, the wings of Drosophila melanogaster beat nearly 200 times per second. The indirect flight muscle fibers that power this movement have evolved to resist the repetitive mechanical stress that results from the 5-ms wing beat cycle at a strain amplitude of 3.5%.