Beta-actin is an isform of actin proteins. Actins are highly conserved proteins that are involved in cell motility, structure, and integrity. There are six different but highly conserved actin isoforms in vertebrates. Four of these isoforms are expressed primarily in striated and smooth muscle cells, whereas the two cytoplasmic β-actin and γ-actin isoforms are ubiquitously expressed. Conserved from birds to mammals, β-actin and γ-actin differ at only four biochemically similar amino acid residues. These amino acid differences confer unique biochemical properties between the two isoforms. Beta-actin is a major constituent of the contractile apparatus. Beta-actin, also known as a “housekeeping” protein, is usually used as a loading control, for among others, the integrity of cells, protein degradation, in PCR and Western blotting. Loading controls are essential for proper interpretation of western blots. They can be used to normalize the levels of protein detected by confirming that protein loading is the same across the gel. Loading controls are usually proteins that exhibit high-level, constitutive expression in the cell type or sample you are examining. This ensures constant expression levels. Thus “housekeeping genes” are frequently chosen for use as loading controls. It is also important that the protein chosen as a loading control has a different molecular weight than the protein of interest so that the bands are distinct and expression levels quantifiable. Popular loading control detection antibodies include anti-β-Actin monoclonal or polyclonal antibodies, anti-COX-4, anti-GAPDH, anti-Tubulin and anti-VDAC/Porin antibodies.