Demonstration of a new glycoprotein Ib-related component in platelet extracts prepared in the presence of leupeptin.
The water-soluble protein glycocalicin is generated during platelet lysis by a proteolytic attack on the integral membrane glycoprotein GP Ib. However, only small amounts of glycocalicin are formed when platelets are solubilized by 1% Triton X-100. Crossed immunoelectrophoresis of such extracts using an antiserum to glycocalicin, shows a continuous immunoprecipitate consisting of two peaks, one representing glycocalicin and the other GP Ib. When leupeptin was present during solubilization, subsequent immunoelectrophoresis revealed yet another GP Ib-related component represented by a third, slow-migrating peak of the immunoprecipitate. During incubation of platelets with dibucaine followed by solubilization in the presence of leupeptin, a gradual transformation of this new form of GP Ib into the previously defined one took place prior to the formation of glycocalicin. An increase followed by a decrease in the agglutination response of the platelets to bovine von Willebrand factor occurred concomitant with these transformations. SDS-polyacrylamide gel electrophoresis of Triton X-100 extracts of platelets did not reveal any difference in the size of GP Ib whether or not leupeptin had been present during the solubilization.
D000818:Animals; D001792:Blood Platelets / Q000032:analysis*; D002417:Cattle; D003902:Detergents; D004591:Electrophoresis, Polyacrylamide Gel; D005169:Factor VIII / Q000302:isolation & purification; D006023:Glycoproteins / Q000097:blood* / Q000302:isolation & purification; D006801:Humans; D007123:Immunoelectrophoresis, Two-Dimensional; D007976:Leupeptins; D008565:Membrane Proteins / Q000097:blood* / Q000302:isolation & purification; D008970:Molecular Weight; D017830:Octoxynol; D009842:Oligopeptides; D010974:Platelet Aggregation; D019038:Platelet Glycoprotein GPIb-IX Complex; D010980:Platelet Membrane Glycoproteins; D011092:Polyethylene Glycols; D012995:Solubility
D003902:Detergents; D006023:Glycoproteins; D007976:Leupeptins; D008565:Membrane Proteins; D009842:Oligopeptides; D019038:Platelet Glycoprotein GPIb-IX Complex; D010980:Platelet Membrane Glycoproteins; C023592:glycocalicin; D011092:Polyethylene Glycols; D005169:Factor VIII; D017830:Octoxynol