Actin is a type of simple protein that is found in the cells of all living organisms. It is an important component of the cytoskeleton, which provides structure and shape to the cell. Actin is also involved in many cellular processes such as cell division, movement, and adhesion. It is a globular protein that is composed of two subunits, alpha and beta, which are connected by a flexible linker region. Actin is essential for the proper functioning of the cell and is found in both prokaryotic and eukaryotic cells.