Platelet glycoprotein Ib: a zinc-dependent binding protein for the heavy chain of high-molecular-weight kininogen

Mol Med. 1999 Aug;5(8):555-63.

Abstract

Domains 3 and 5 of high-molecular-weight kininogen (HK) have been shown to bind to platelets in a zinc-dependent reaction. However, the platelet-binding proteins responsible for this interaction have not been identified. We have focused on the platelet-binding site for the heavy chain (domain 3), which we approached using a domain 3-derived peptide ligand and isolated binding proteins by affinity chromatography. The domain 3-derived peptide, thrombin, HK, factor XII, as well as antibody to glycocalicin (the N-terminal portion of the alpha chain of GPIb) recognized a protein at 74 kD. We also isolated the thrombin receptor (PAR 1) at 45 kD, however, none of the above-mentioned ligands bound to this protein. Isolation of platelet membrane proteins using a monoclonal anti-glycocalicin antibody column revealed the same HK binding protein at 74 kD, which was reactive with anti-GPIb and represents a GPIb fragment. By photoaffinity labeling, HK interacted with membrane GPIb, which was then isolated in native form (135 kD) along with gC1qR, a ligand for the HK light chain. Finally, (125)I-HK binding to platelets was significantly inhibited by the anti-GPIb antibody. These results suggest that the GPIb alpha chain, a known thrombin binding protein, is also one of the zinc-dependent platelet membrane binding sites for HK domain 3.

MeSH terms

  • Antibodies
  • Biotinylation
  • Blood Platelets / metabolism*
  • Cell Membrane / metabolism
  • Chromatography, Affinity
  • Electrophoresis, Polyacrylamide Gel
  • Factor XII / metabolism*
  • Humans
  • Kinetics
  • Kininogen, High-Molecular-Weight / blood*
  • Molecular Weight
  • Platelet Glycoprotein GPIb-IX Complex / immunology
  • Platelet Glycoprotein GPIb-IX Complex / isolation & purification
  • Platelet Glycoprotein GPIb-IX Complex / metabolism*
  • Thrombin / metabolism
  • Zinc / metabolism*
  • Zinc / pharmacology

Substances

  • Antibodies
  • Kininogen, High-Molecular-Weight
  • Platelet Glycoprotein GPIb-IX Complex
  • glycocalicin
  • Factor XII
  • Thrombin
  • Zinc