Actins are highly conserved cytoskeletal proteins that are ubiquitously expressed in all eukaryotic cells. There are 6 known isoforms of actin in mammals. Nonmuscle β- and γ-actin, also known as cytoplasmic actin, are predominantly expressed in nonmuscle cells, controlling cell structure and motility. Two smooth muscle actins, α- and γ-actin, are found primarily in vascular smooth muscle and enteric smooth muscle, respectively. α-cardiac and α-skeletal actin are expressed in striated cardiac and skeletal muscles, respectively. Actin can be present as either a free monomer called G-actin (globular) or as part of a linear polymer microfilament called F-actin (filamentous), both of which are essential for cellular functions such as the mobility and contraction of cells during cell division.