Relationship between glycocalicin and glycoprotein Ib of human platelets.

Abstract

Asialoglycoprotein lb and asialoglycocalicin have been isolated from the membranes and from the supernatant, respectively, after sonication of neuraminidase-treated platelets, by lectin affinity chromatography on peanut agglutinin. The isolated asialoglycoprotein lb had an apparent molecular weight of 160,000 when not reduced and 150,000 when reduced, whereas the asialoglycocalicin had an apparent molecular weight of 150,000, both reduced and unreduced, on sodium dodecyl sulfate/polyacrylamide gel electrophoresis. Both preparations contained only trace amounts of impurities. The asialoglycoprotein lb and asialoglycocalicin in both the unreduced and reduced states were separated by gel electrophoresis, radioiodinated in gel slices, and digested with trypsin, and the digests were analyzed by two-dimensional high-voltage electrophoresis and thin-layer chromatography followed by autoradiography. The tryptic peptide maps showed great similarities between glycocalicin and glycoprotein lb, with the latter (both unreduced and reduced) containing additional peptides, supporting the idea that glycocalicin is derived from glycoprotein lb. The unreduced glycoprotein Ib contained additional peptides compared to the reduced due to the disulfide-bond-linked (3com-ponent. There were also slight differences between unreduced and reduced glycocalicin, indicating that at least one intramolecular disulfide bond is present.

Surface modifications in the platelets of a patient with alpha-N-acetyl-D-galactosamine residues, the Tn-syndrome.

“…The principal sugars were found to be galactose, Nacetylglucosamine, GalNAc and sialic acid in a ratio (2:1:1:2) with serine and threonine among the most abundant amino acids. The recent studies of Clemetson et al (34) have shown that there were great similarities between the tryptic peptide maps of asialoglycocalicin and asialo-GP Iba. It appears that the site of action of the Ca2+-dependent protease that cleaves glycocalicin from GP Ib, is not too distant from the disulfides the cleavage of which separates Iba and Ib,B.…”

“…The lectin, peanut agglutinin (Arachis hypogaea) has anti-T specificity (46), binding to terminal galactose residues in glycoproteins. Studies on the binding of 1251-labeled lectins to platelet membrane glycoproteins separated by SDS-PAGE have indicated that peanut agglutinin binds specifically to GP Iba when neuraminidase-treated platelets are being analyzed (34,47). These observations collectively suggest a partial similarity between the oligosaccharide chain composition of platelet GP Ib and the MN-sialoglycoprotein of erythrocytes.…”

“…Two-dimensional SDS-PAGE analysis. GP lb of normal platelets is a high molecular weight GP composed of two subunit chains linked by one or more disulfide bonds (20,34). On disulfide reduction a large a-subunit (Mr 143,000) is separated from a smaller A-subunit (Mr 22,000) (20).…”

Purification of thrombospondin receptor (CD36) from human platelet membrane

“…Trypsinized platelet membrane was then solubilized using Triton X-114 and detergent phase was subjected to WGA-affinity chromatography ( Figure 2). Lectins have been shown to specifically recognize and bind to certain glycoproteins and this specific interaction between lectins and glycoproteins has been successfully used in the purification of platelet membrane glycoproteins (Clemetson et al, 1981, Leung et al, 1981. A combination of various immobilized lectins with different binding characteristics was revealed to be very effective for the purification of glycoproteins.…”

Characterization of a human lymphocyte surface sialoglycoprotein that is defective in Wiskott-Aldrich syndrome.

“…Like gpL115, GPIb and its soluble form glycocalicin (8) adhere to wheat germ lectin (7) and asialo-GPIb adheres to peanut lectin (8). GPIb (glycocalicin) consists to 60% of carbohydrate that appears to be exclusively mucin-type units linked to serine and threonine (7,42).…”