With microtubules, it is a key component of the cytoskeleton, where it forms microfilaments.
In the presence of calcium ions, the hydrophobic cleft between subdomains 1 and 3 of this protein is bound to by gelsolin. The Arp2/3 complex causes branching in this protein and is activated by WASp/Scar proteins. The ADF/cofilin family of proteins twists it, resulting in the loss of its phalloidin-binding site. A steady state condition associated with nucleotide hydrolysis in this protein is called treadmilling. Its polarity can be determined with S1 fragments, which give this protein's plus and minus ends a barbed or arrowhead "decoration," respectively. Tropomodulins and CapZ cap its two ends. The globular, or G, form of this protein is polymerized helically to form its F form. With microtubules, it is a key component of the cytoskeleton, where it forms microfilaments. For 10 points, name this protein which forms the thin filament in sarcomeres, where it is found with myosin.
In the presence of calcium ions, the hydrophobic cleft between subdomains 1 and 3 of this protein is bound to by gelsolin.
actin