Summary
Membrane glycoproteins IIb and IIIa play a major role in human blood platelet aggregation.
The absence or the severe reduction of these two membrane glycoproteins, as observed
in platelets of Glanzmann’s thrombasthenic patients, is related to a lack of platelet
aggregation. Separation of Glanzmann’s thrombasthenic platelet samples by two-dimensional
polyacrylamide O’Farrell gels show the absence of a high and several low molecular
mass glycoproteins, in addition to the loss of glycoproteins IIb and IIIa (McGregor
J. L. et al. Eur. J. Biochem. 1981; 116: 379-388). The aim of this study was to identify
the nature of the high molecular mass component, absent in thrombasthenic platelets.
A high molecular mass glycoprotein (200 kDa), present in two-dimensional SDS-polyacrylamide
O-Farrell gel separations, was recognized by a monoclonal antibody (MP37) directed
against glycoprotein IIIa. Moreover, the tryptic peptide map of this high molecular
mass glycoprotein was nearly identical to that of glycoprotein IIIa. These results
indicate that this high molecular mass glycoprotein present in SDS-polyacrylamide
gels is a dimer of glycoprotein IIIa. This work raises the possibility that the high
molecular mass glycoprotein, absent in two-dimensional O’Farrell gel separations of
thrombasthenic platelets, is a dimer of glycoprotein IIIa.
Key words
Platelets - Glycoprotein IIIa - Glycoprotein IIIa dimer - Tryptic peptide maps - Monoclonal
antibody MP37
