Actin, aortic smooth muscle is one of six different actin isoforms which have been identified. Six different actin isoforms have been identified in vertebrates by amino acid sequencing: skeletal muscle, cardiac muscle, 2 smooth muscle (enteric and aortic), and 2 cytoplasmic (beta and gamma) (Vandekerckhove and Weber, 1979). Their amino acid sequences are similar and well conserved in evolution; e.g., skeletal and cardiac actins differ by only 4 amino acids, and skeletal muscle and cytoplasmic beta-actins differ by only 25 amino acids out of a total of 374.

Ueyama et al. (1984) isolated and characterized the human aortic smooth muscle actin gene. The gene has a transition point mutation in position 309, substituting thymine for cytosine.