Determination of the vitronectin binding site on plasminogen activator inhibitor 1 (PAI‐1)

Vitronectin is the carrier protein of plasminogen activator inhibitor 1 (PAI-1). We used a well-characterized panel of anti-human PAI-1 monoclonal antibodies (MoAbs) to localize the vitronectin-binding site on PAI-1. By employing a direct vitronectin/PAI-1 binding assay and two vitronectin-dependent inhibition assays, we demonstrate that the anti-PAI-1 MoAbs CLB-5, CLB-10, CLB-2C8 and I1, directed against different epitopes in the region between amino acids 110 and 145, prevent the interaction of PAI-1 with vitronectin. We conclude that the region between amino acids 110 and 145 of PAI-1 harbours an important determinant for the interaction with vitronectin.