Roles of Titin in the Structure and Elasticity of the Sarcomere

The giant protein titin is thought to play major roles in the assembly and function of muscle sarcomeres. Structural details, such as widths of Z- and M-lines and periodicities in the thick filaments, correlate with the substructure in the respective regions of the titin molecule. Sarcomere rest length, its operating range of lengths, and passive elastic properties are also directly controlled by the properties of titin. Here we review some recent titin data and discuss its implications for sarcomere architecture and elasticity

Making Muscle Elastic: The Structural Basis of Myomesin Stretching

The muscle M-band protein myomesin comprises a 36-nm long filament made of repetitive immunoglobulin–helix modules that can stretch to 2.5-fold this length, demonstrating substantial molecular elasticity

Schematics of sarcomere and M-band structure derived from electron microscopy of muscle [<b>1]</b>,[2<b> </b>].

<p>(a) Relaxed sarcomere. (b) After isometric contraction causing tension in the M-band and sliding between thick filaments; (c) M-band model showing M-bridges connecting thick filaments, as well as additional links connecting M-bridges.</p