Functions
Actin forms microfilaments which are typically one of the most dynamic of the three subclasses of the eukaryotic cytoskeleton.
In turn, this gives actin major functions in cells:
- To form microfilaments to give mechanical support to cells, and provide trafficking routes through the cytoplasm to support signal transduction
- To allow cell motility in cells which undergo amoeboid motion using pseudopods (see actoclampin molecular motors) and phagocytosis, for example of bacteria by macrophages
- In metazoan muscle cells, to be the scaffold on which myosin proteins generate force to support muscle contraction
- In nonmuscle cells, to be a track for cargo transport myosins (nonconventional myosins) such as myosin V and VI. Nonconventional myosins use ATP hydrolysis to transport cargo, such as vesicles and organelles, in a directed fashion much faster than diffusion. Myosin V walks towards the barbed end of actin filaments, while myosin VI walks toward the pointed end. Most actin filaments are arranged with the barbed end toward the cellular membrane and the pointed end toward the cellular interior. This arrangement allows myosin V to be an effective motor for export of cargos, and myosin VI to be an effective motor for import.
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