Divalent cation-dependent structure in the platelet membrane glycoprotein Ia-IIa (VLA-2) complex.
Recent studies have shown that the platelet membrane glycoprotein Ia-IIa (VLA-2) complex mediates the Mg(++)-dependent adhesion of platelets to collagen and that this adhesion is inhibited by Ca++ in a simple, linear, noncompetitive manner. These findings suggested that separate binding sites for Mg++ and Ca++ stabilize different divalent cation-dependent structures within the receptor complex. To provide evidence for the existence of such structures purified platelet Ia-IIa complex was subjected to limited proteolytic digestion in the presence of Mg++, Ca++, Mg++ and Ca++, or EDTA and the resulting peptides mapped by SDS-PAGE using both one and two-dimensional techniques. Unique patterns of tryptic peptides were produced under each of the conditions. The results indicate that Mg++ and Ca++ stabilize different structures within the Ia-IIa (VLA-2) complex and that these structures influence both the collagen binding activity and proteolytic susceptibility of the complex.
Staatz
W D
WD
Department of Pathology, Washington University School of Medicine, St. Louis, MO 63110.
Peters
K J
KJ
Santoro
S A
SA
D001792:Blood Platelets / Q000648:ultrastructure*; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D010449:Peptide Mapping; D010980:Platelet Membrane Glycoproteins / Q000648:ultrastructure*; D016029:Receptors, Very Late Antigen / Q000648:ultrastructure*; D014357:Trypsin / Q000494:pharmacology
D002413:Cations, Divalent; D010980:Platelet Membrane Glycoproteins; D016029:Receptors, Very Late Antigen; D014357:Trypsin; D008274:Magnesium; D002118:Calcium