LOCALIZATION OF A VITRONECTIN BINDING REGION OF PLASMINOGEN-ACTIVATORINHIBITOR-1

The PAI-1 binding site for VN was studied using two independent method s. PAI-1 was cleaved by Staph V8 protease, producing 8 frag ments, onl y 2 of which bound to [I-125]-VN. These fragments were predicted to ov erlap between residues 91-130. Since PAI-2 has structural homology to PAI-1, but does not bind to vitronectin, chimeras of PAI-1 acid PAI-2 were constructed. Four chimeras, containing PAI-1 residues 1-70, 1-105 , 1-114, and 1-167 were constructed and expressed in vitro. PAI-1, PAI -2, and all of the chimeras retained inhibitory activity for t-PA, but only the chimera containing PAI-1 residues 1-167 formed a complex wit h VN. Together, these results predict that the VN binding site of PAI- 1 is between residues 115-130.