Ca sup 2+ -dependent binding of a synthetic Arg-Gly-Asp (RGD) peptide to a single site on the purified platelet glycoprotein IIb-IIIa complex
- F. Hoffmann-La Roche and Co., Basel (Switzerland)
The platelet glycoprotein IIb-IIIa complex (GP IIb-IIIa) is a member of the integrin receptor family that recognizes adhesive proteins containing the Arg-Gly-Asp (RGD) sequence. In the present study the binding characteristics of the synthetic hexapeptide Tyr-Asn-Arg-Gly-Asp-Ser (YNRGDS, a sequence present in the fibrinogen alpha-chain at position 570-575) to purified GP IIb-IIIa were determined by equilibrium dialysis. The binding of 125I-YNRGDS to GP IIb-IIIa was specific, saturable, and reversible. The apparent dissociation constant was 1.0 +/- 0.2 microM, and the maximal binding capacity was 0.92 +/- 0.02 mol of 125I-YNRGDS/mol of GP IIb-IIIa, indicating that GP IIb-IIIa contains a single binding site for RGD peptides. The binding of 125I-YNRGDS to purified GP IIb-IIIa showed many of the characteristics of fibrinogen binding to activated platelets: the binding was inhibited by fibrinogen, by the monoclonal antibody A2A9, and by the dodecapeptide from the C terminus of the fibrinogen gamma-chain. In addition, the binding of 125I-YNRGDS to GP IIb-IIIa was divalent cation-dependent. Our data suggest that two divalent cation binding sites must be occupied for YNRGDS to bind: one site is specific for calcium and is saturated at 1 microM free Ca2+, whereas the other site is less specific and reaches saturation at millimolar concentrations of either Ca2+ or Mg2+. The results of the present study support the hypothesis that the RGD domains within the adhesive proteins are responsible for their binding to GP IIb-IIIa.
- OSTI ID:
- 5478953
- Journal Information:
- Journal of Biological Chemistry; (USA), Journal Name: Journal of Biological Chemistry; (USA) Vol. 264:22; ISSN JBCHA; ISSN 0021-9258
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ADHESION
ALKALINE EARTH METAL COMPOUNDS
AMINO ACID SEQUENCE
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BLOOD COAGULATION FACTORS
BLOOD PLATELETS
BODY FLUIDS
CALCIUM COMPOUNDS
COAGULANTS
DAYS LIVING RADIOISOTOPES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
FIBRINOGEN
GLOBULINS
GLYCOPROTEINS
HEMATOLOGIC AGENTS
HEMOSTATICS
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
MAGNESIUM COMPOUNDS
MATERIALS
MEMBRANE PROTEINS
MOLECULAR STRUCTURE
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PEPTIDES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
TRACER TECHNIQUES