Mouse Monoclonal Antibody to all Actin Isotypes
Cat# MCA-5J11

      Actin is one of the most abundant and highly conserved proteins of eukaryotes (1-5). Mammalian actins are the product of six distinct but closely related genes with differing distribution patterns in cell types and in tissues. The amino acid sequences of the six human actin gene products are 94-97% identical, so antibodies which bind all six gene products are to be expected. A sequence alignment of the six human actin can be downloaded from here. The molecular weight of all six proteins is ~42kDa, and one or more actins is found in essentially every type of crude cellular and tissue extract. As a result, antibodies to actin are widely used as western blotting standards to verify that the various steps of the western blotting procedure have been performed correctly. In addition, actin is regarded as a “house keeping” protein which is generally not altered in expression as a result of experimental manipulations. Thus, quantification of the actin band on a western blot can be used as a loading control. The actin isotypes were originally classified as α, β and γ since three different actin spots were detected by 2-dimensional SDS-PAGE. Subsequently, the α spot was found to potentially contain three actin gene products, α-skeletal actin, α-vascular smooth muscle actin and α-cardiac muscle actin. The β spot contained a single protein called simply β-actin while the γ spot may contain either γ-1 and/or γ-2 actin, which are enteric and smooth muscle actins respectively. The six mammalian gene products are between 94 and 97% identical, with most of the variability seen at the N-terminus (2). Despite the similarity between the 6 gene products there is some evidence of functional differences between them (6). Actin cycles between monomeric (G-actin) and polymeric microfilaments (F-actin) in a highly regulated manner under the influence of a variety of actin capping and severing proteins the Rho family GTPases, the various Rac, Rho and CDC42 proteins (7).
      The MCA-5J11 was made against an actin preparation derived from bovine brain. We have shown that MCA-5J11 binds all six actin gene products, (see supplemental data here), not unexpected given the 94-97% amino acid identity of the 6 proteins. As a result MCA-5J11 will detect all actin proteins present in any mammalian cell or tissue extract, making it a useful and versatile western blotting standard. MCA-5J11 works well for IF, ICC and IHC (see data under “Additional Info” tab). Mouse select image at left for larger view.