Conformational lability of vitronectin: induction of an antigenic change by alpha-thrombin-serpin complexes and by proteolytically modified thrombin

Biochemistry. 1989 Sep 19;28(19):7617-23. doi: 10.1021/bi00445a017.


We previously showed that the alpha-thrombin-antithrombin III complex causes antigenic change in vitronectin as monitored by the monoclonal anti-vitronectin antibody 8E6 (Tomasini & Mosher, 1988). We have extended these studies to other protease-serpin complexes and to gamma-thrombin, a proteolytic derivative of alpha-thrombin. In the presence of heparin, recognition of vitronectin by 8E6 was increased 64- or 52-fold by interaction with the complex of alpha-thrombin and heparin cofactor II or the Pittsburgh mutant (Met358----Arg) of alpha 1-protease inhibitor, respectively. This was comparable to the value obtained with the alpha-thrombin-antithrombin III complex. Factor Xa-serpin complexes were approximately 4-fold less effective than the corresponding thrombin complexes. alpha-Thrombin-serpin complexes but not Xa-serpin complexes formed disulfide-bonded complexes with vitronectin. Antigenic changes and disulfide-bonded complexes were not detected when trypsin- or chymotrypsin-serpin complexes were incubated with vitronectin. gamma-Thrombin caused 7- and 34-fold increases in recognition of vitronectin by MaVN 8E6 in the absence and presence of heparin, respectively. In contrast, alpha-thrombin by itself had no effect. The antigenic change induced by gamma-thrombin was maximal when gamma-thrombin and vitronectin were equimolar, was not dependent on cleavage of vitronectin, and was abolished by inhibition of gamma-thrombin with Phe-Pro-Arg-chloromethyl ketone but not with diisopropyl fluorophosphate. These data indicate that alpha-thrombin is the component in alpha-thrombin-serpin complexes that induces the antigenic change in vitronectin, probably via a region that is preferentially exposed in gamma-thrombin.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antibodies, Monoclonal / immunology
  • Antigens / immunology
  • Blood Proteins / isolation & purification
  • Blood Proteins / metabolism*
  • Disulfides / pharmacokinetics
  • Enzyme-Linked Immunosorbent Assay
  • Glycoproteins / isolation & purification
  • Glycoproteins / metabolism*
  • Goats
  • Heparin / pharmacokinetics
  • Immunoblotting
  • Mice
  • Protease Inhibitors / pharmacokinetics*
  • Protein Conformation / drug effects
  • Rabbits
  • Serpins / pharmacokinetics*
  • Solubility
  • Substrate Specificity / drug effects
  • Thrombin / antagonists & inhibitors
  • Thrombin / immunology
  • Vitronectin


  • Antibodies, Monoclonal
  • Antigens
  • Blood Proteins
  • Disulfides
  • Glycoproteins
  • Protease Inhibitors
  • Serpins
  • Vitronectin
  • Heparin
  • Thrombin