Actinin

α-Actinin is an actin-binding protein present in both muscle and non-muscle cells. It has a polypeptide molecular weight of 100 kD and forms dimers in solution. In normal skeletal muscle, α-actinin is associated with the Z-discs that define the muscle sarcomers. In smooth muscle, α-actinin is detected predominantly in dense bodies and plaques, which are characteristic of that tissue. Immunofluorescent labeling of a large variety of cells with anti α-actinin reveals an extensive association of the proteins with the actin containing stress fibers and, in particular, with their membrane-bound termini.