Cofilin severs filaments to cause depolymerization proximally. Non-muscle Myosin Many types of myosin exist. All have a characteristic motor domain. The motor domain has actin-activated ATPase, can move actin filaments, and has a characteristic amino acid sequence. Types differ widely from each other in their tails.
Tails presumably bind to specific other molecules that are the cargo.
Also, multiple isoforms of each type can exist even in one cell. Forms bipolar filaments in vitro, similar to but smaller than muscle thick filaments. Bipolar arrangement implies contraction - pulling two actin filaments together by walking toward the barbed ends. Stress fibers Similar to myofibrils. Bundles of actin filaments with periodic distribution of myosin, a -actinin, and tropomyosin.