Anti-(Arg-Gly-Asp-Ser) antibody and its interaction with fibronectin, fibrinogen and platelets.
An antibody population recognizing the sequence Arg-Gly-Asp-Ser (RGDS) in fibronectin, anti-(RGDS)N, was isolated by immunoadsorption. Between 2.5% and 4.9% of antibodies were obtained from two different anti-fibronectin sera indicating that this region represents an antigenic epitope in native fibronectin. Complete inhibition of binding of 125I-fibronectin to anti-(RGDS)N was produced only by nonreduced and reduced fibronectin. Fibrinogen and synthetic RGDS tetrapeptide, each at concentration of 10 microM, showed only a slight inhibition of 22% and 17%, respectively. Measurements of the conformational constant, the equilibrium constant for the interconversion of the non-native and native conformations of this epitope, showed that less than 0.0001% of the RGDS molecules adopt the native conformation in aqueous solutions. It indicates that long-range interactions in fibronectin and fibrinogen result in different conformations of the RGDS sequence in both proteins. Anti-(RGDS)N antibodies purified from anti-fibronectin serum had a strong inhibitory effect on thrombin-stimulated platelet aggregation. They also inhibited binding of fibronectin and fibrinogen to thrombin-stimulated platelets, supporting the primary role of the RGDS sequence in the direct interaction of these proteins with platelet membrane receptors.
Cierniewski
C S
CS
Department of Biophysics, Institute of Physiology and Biochemistry, Medical School, Lodz, Poland.
Swiatkowska
M
M
Poniatowski
J
J
Niewiarowska
J
J
D000906:Antibodies / Q000494:pharmacology*; D000918:Antibody Specificity; D001666:Binding Sites, Antibody / Q000187:drug effects; D001792:Blood Platelets / Q000276:immunology* / Q000502:physiology; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000032:analysis; D005340:Fibrinogen / Q000276:immunology*; D005353:Fibronectins / Q000276:immunology*; D006801:Humans; D007106:Immune Sera / Q000032:analysis; D007120:Immunochemistry; D009842:Oligopeptides / Q000276:immunology*; D010974:Platelet Aggregation / Q000187:drug effects*; D011487:Protein Conformation; D013917:Thrombin / Q000037:antagonists & inhibitors / Q000494:pharmacology
D000906:Antibodies; D000939:Epitopes; D005353:Fibronectins; D007106:Immune Sera; D009842:Oligopeptides; D005340:Fibrinogen; C046617:arginyl-glycyl-aspartyl-serine; D013917:Thrombin