Actins are highly conserved proteins involved in cell motility, structure and integrity. Actin has been found to be expressed in at least six isomeric forms. It is expressed in heart and skeletal striated muscle tissue, and in certain smooth muscle tissues, regulating contractile potentials for these cells. It is also expressed in the cytoplasm of non-muscle cells, functioning to control cell structure and motility. Beta actin is usually used as a loading control, for among others, the integrity of cells, protein degradation, in Western Blotting.