Plasminogen activator inhibitor-1 polymers, induced by inactivating amphipathic organochemical ligands.
Negatively charged organochemical inactivators of the anti-proteolytic activity of plasminogen activator inhibitor-1 (PAI-1) convert it to inactive polymers. As investigated by native gel electrophoresis, the size of the PAI-1 polymers ranged from dimers to multimers of more than 20 units. As compared with native PAI-1, the polymers exhibited an increased resistance to temperature-induced unfolding. Polymerization was associated with specific changes in patterns of digestion with non-target proteases. During incubation with urokinase-type plasminogen activator, the polymers were slowly converted to reactive centre-cleaved monomers, indicating substrate behaviour of the terminal PAI-1 molecules in the polymers. A quadruple mutant of PAI-1 with a retarded rate of latency transition also had a retarded rate of polymerization. Studying a number of serpins by native gel electrophoresis, ligand-induced polymerization was observed only with PAI-1 and heparin cofactor II, which were also able to copolymerize. On the basis of these results, we suggest that the binding of ligands in a specific region of PAI-1 leads to so-called loop-sheet polymerization, in which the reactive centre loop of one molecule binds to beta-sheet A in another molecule. Induction of serpin polymerization by small organochemical ligands is a novel finding and is of protein chemical interest in relation to pathological protein polymerization in general.
Pedersen
Katrine E
KE
Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10, Denmark. kep@mb.au.dk
Einholm
Anja P
AP
Christensen
Anni
A
Schack
Lotte
L
Wind
Troels
T
Kenney
John M
JM
Andreasen
Peter A
PA
D000595:Amino Acid Sequence; D001665:Binding Sites; D001704:Biopolymers / Q000737:chemistry / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D015844:Heparin Cofactor II / Q000494:pharmacology; D006358:Hot Temperature; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010206:Papain / Q000378:metabolism; D017395:Plasminogen Activator Inhibitor 1 / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015843:Serpins / Q000378:metabolism; D013050:Spectrometry, Fluorescence / Q000379:methods; D014568:Urokinase-Type Plasminogen Activator / Q000494:pharmacology
D001704:Biopolymers; D008024:Ligands; D017395:Plasminogen Activator Inhibitor 1; D011994:Recombinant Proteins; D015843:Serpins; D015844:Heparin Cofactor II; D014568:Urokinase-Type Plasminogen Activator; D010206:Papain