title: Cleavage of thrombosthenin A by thrombin. Evidence for the existence of two types of bovine platelet actin.
abstract: Bovin platelet actin prepared by Spudich's method (Spudich, J. A. (1972) Cold Spring Harbor Symp. Quant. Biol. 27, 585-594) separated into two peaks on a Sephadex G-200 column. The actin of both peaks had a mol. wt. of 42 000 on sodium dodecyl sulfate-polyacrylamide gel and activated myosin ATPase, although in a quantitatively different manner. Actin eluted in the first peak (probably an oligomeric form) was not polymerized in 2 mM MgCl2 and 0.05 M KCl, while that of the second peak went through normal G-F transformation. If CaATP was present in the incubation mixture neither actin was attacked by thrombin. However, if EDTA was added, thrombin split G-actins and the pattern of cleavage was the same as that found for muscle actin in our earlier studies, i.e. the final split products were two actinopeptides and two larger fragments of 26 500 and 11 000 daltons. It is suggested that the possible attraction of membrane-associated platelet actin for thrombin may have an importance in thrombin-induced platelet aggregation.
mesh_terms: D000199:Actins / Q000302:isolation & purification / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism*; D002417:Cattle; D004492:Edetic Acid / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D008970:Molecular Weight; D009218:Myosins / Q000378:metabolism; D013917:Thrombin / Q000378:metabolism*
chemical_list: D000199:Actins; D001798:Blood Proteins; D004492:Edetic Acid; D013917:Thrombin; D000251:Adenosine Triphosphatases; D009218:Myosins