Structure and function of platelet membrane glycoproteins-analysis of their mechanism using gene analysis and affinity labelling

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1. Polymorphism of platelet membrane glycoprotein Ib and its physiological function-Glycocalicin, a degraded form of GPIb,was purified and further degraded by various kinds of proteases. polymorphism of GPIb was found to be derived from glycopeptide portion of 90kDa. Polymorphysm of GPIb of patients with brain thombosis was analyzed. Although number is rather small(n=18), type C GPIb was found to be more and type D was found to be less in the patient than in the normal Japanese subjects. The relationship between the occurence of thrombosis and type C GPIb should be confirmed by using a larger number of patients.2. Biosynthesis of platelet glycoproteins-Megakaryoblast cell line was found to express GPIb,II b and IIIa antigens. Precursors of GPIb and GPII b were found in the different subfractions from plasma membrane fraction.3. Thrombasthenia with precursor type GPII b-We found 2 different families of patients with thrombasthenia who have an abnormal GPII b with larger molecular weight. This abnormal GPII b was identified as a precrsor of GPII b which was mentioned above. Analysis of the abnormal GPII b in these patients would give us useful infomation for understanding the mechanism of biosynthesis of GPII b and IIIa.