Actin is a globular moonlighting protein (able to perform more than one function), sometimes called G Actin and in its beta and gamma isoform is a subunit of cell microfilaments, one of the key elements of the cytoskeleton.
G Actin subunits assemble into long polymers F Actin which entwine to form a double helix structure.
In its microfilament form in the cytoskeleton the cell benefits from mechanical support and transmission tunnels for signal transduction.