The vitronectin binding area of plasminogen activator inhibitor-1, mapped by mutagenesis and protection against an inactivating organochemical ligand

Abstract

A distinguishing feature of serpins is their ability to undergo a conformational change consisting in insertion of the reactive centre loop (RCL) into β-sheet A. In the serpin plasminogen activator inhibitor-1 (PAI-1), RCL movements are regulated by vitronectin, having a previously poorly defined binding site lateral to PAI-1’s β-sheet A. Using a novel strategy, based on identification of amino acid residues necessary for vitronectin protection of PAI-1 against inactivation by 4,4′-dianilino-1,1′-bisnaphthyl-5,5′-disulfonic acid, we have defined a vitronectin binding surface spanning 10 residues between α-helix F, β-strand 2A, and α-helix E. Our results contribute to elucidating the unique serpin conformational change.