Beta actin also know as Cytoplasmic Actin is a 42 kDa, highly conserved protein, ubiquitously expressed in all eukaryotic cells. They comprise, along with microtubules, a major component of the cytoskeleton. β-Actin is a relatively stable cytoskeletal protein normally at a constant level in cells, regardless of experimental treatment or technical procedure. For this reason, measurement of β -Actin is generally used as an internal control for experimental error.