J. Biol. Chem., Vol. 261, Issue 16, 7230-7235, Jun, 1986
Identification of the immunoglobulin G receptor of human platelets
M Steiner and EF Luscher
The binding site of IgG on human platelets was studied by the use of the
cleavable heterobifunctional cross-linking agent N-succinimidyl (4-
azidophenyldithio)propionate. Binding characteristics of the derivatized
IgG were similar to normal IgG. Periodate-borohydride treatment of
platelets also did not significantly alter their ability to bind IgG.
N-Succinimidyl (4-azidophenyldithio)propionate was bound to IgG via a
succinimidyl ester and then photolyzed in the presence of intact platelets.
Their membrane glycoproteins were first tritiated by the
periodate-borohydride method. The cross-linked product was analyzed by two
dimensional sodium dodecyl sulfate-polyacrylamide gradient gel
electrophoresis. The non-reduced first-dimension gels were subjected to 5%
2-mercaptoethanol prior to separation in the second dimension. Such gels
were then evaluated by fluorography, silver staining, and counting the
radioactivity of sequential gel strips in the area of cross- linking. The
protein complexes at the interface between stacking and running gel were
further resolved in isoelectric focusing gels. One IgG- containing band
could be identified. After reduction, the constituent proteins of the
cross-linked complex were analyzed by sodium dodecyl sulfate-polyacrylamide
gradient gel electrophoresis and subsequent immunoblotting with an
antiserum against platelet membrane glycoproteins. All of these studies
gave evidence of glycoprotein IIIa as the receptor of IgG. Based on the
results of the different experimental approaches, we conclude that
glycoprotein IIIa is the IgG receptor in human platelets.
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