In vitro Incorporation of Amino-acids into the Contractile Protein of Human Blood Platelets

Abstract

BLOOD platelets contain a considerable concentration of protein of which about 21 per cent can be accounted for by fibrinogen, serum albumin and a glycogen–globulin complex¹. Most of the protein of the platelet consists of the specific contractile protein, thrombosthenin^2,3, and other uncharacterized protein¹. The origin of platelet proteins has not been established, but it is likely that albumin and fibrinogen originate in plasma, although no other plasma proteins have been detected in platelets¹. Platelets are formed by fragmentation of the megakaryocyte^4–6 and do not contain a nucleus. It is possible that the contractile as well as other proteins are already present in the cytoplasm during the maturation of the megakaryocyte. It is also possible that certain proteins are synthesized by the platelet in which ribosomes have been observed⁷. This communication reports the incorporation of amino-acids labelled with carbon-14 into the contractile protein of human blood platelets.