Polymorphism of α‐actinin from human blood platelets Homodimeric and heterodimeric forms

Abstract

In purified solutions of α‐actinin from human blood platelets, three polypeptides a, b and c, of approximately 100 kDa, were observed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. They were identified as α‐actinin subunits on the basis of their cross‐reactivity with antibodies against skeletal muscle α‐actinin and their interaction with F‐actin. After electrophoresis in the absence of sodium dodecyl sulfate, six forms were observed: aa, ab, bb, ac, bc, cc. The similarity between the one‐dimensional peptide maps of a and b and the absence of b in the presence of calcium‐dependent protease inhibitors indicated that b is probably derived from the a subunit. The c subunit differs from the a subunit. The results provide evidence that there are actually only two platelet α‐actinin subunits a and c which give rise to three isoforms: two homodimers aa and cc, and one heterodimer ac.