![](https://cos-cdn.shuashuati.com/pipixue-wap/2020-1230-1107-56/ti_inject-812ce.png)
The thin actin filaments are attached at one end to the Z disk in a regular pattern in the myofibrils. The assembly includes the minor muscle proteins α-actinin, desmin, and vimentin. Thin filaments also contain a large protein called _______ (~7,000 amino acid residues), thought to be structured as an α helix that is long enough to span the length of the filament.