Evidence for the presence of tropomyosin in the cytoskeletons of ADP- and thrombin-stimulated blood platelets

Stimulation of porcine platelets with ADP or thrombin and subsequent analyses of their cytoskeletons by SDS-polyacrylamide gel electrophoresis have shown the presence of a 30.5-kDa polypeptide in the cytoskeletons of activated as well as aggregated platelets. This polypeptide comigrates with pure porcine platelet tropomyosin in SDS gels, their mobilities being similarly and markedly decreased in the presence of 6 M urea. One-dimensional peptide mapping after limited proteolysis by Staphylococcus aureus protease gives the same pattern for pure tropomyosin and the 30.5-kDa polypeptide. This latter may thus be identified as the porcine platelet tropomyosin subunit, the role of which may not be solely structural.