Spectrins are central components of the cytoskeleton that form a scaffold below the plasma membrane. Spectrins contain two subunits, alpha and ß, which intertwine to form heterodimers that can self associate into elongated tetramers. alpha-spectin I and ß-spectrin I form heterodimers in red blood cells, while nonerythroid mammalian cells contain heterodimers of alpha-spectin I and II with ß-spectrin I to V. The structure of spectrins includes a succession of triple-helical repeats alongwith various domains, such as SH3 domain, EF hands, PH domains, and binding domains for ankyrin, actin, band 4.1, and calmodulin. alpha-spectrin II is a widely expressed non-erythroid alpha-spectrin that contains an SH3 domain, a calmodulin binding site, and two cleavage sites for proteases, such as calpains and caspase-3. ß-spectrin II is a widely expressed non-erythroid ß-spectrin that contains a C-terminal region that interacts with alpha-spectrins and a PH domain. alpha-spectrin II and ß-spectrin II, like many other spectrins, can form heterodimers that can self associate into tetramers, as well as interact with Band 4.1, F-actin, and other proteins near the plasma membrane. This scaffold of cytoskeletal and plasma membrane proteins is critical for the maintenance of cell structure. This antibody is routinely tested by the Western blot analysis.