Distinct encounter complexes of PAI-1 with plasminogen activators and vitronectin revealed by changes in the conformation and dynamics of the reactive center loop.

摘要: UNLABELLED Plasminogen activator inhibitor-1 (PAI-1) is a biologically important serine protease inhibitor (serpin) that, when overexpressed, associated with high risk for cardiovascular disease and cancer metastasis. Several of its ligands, including vitronectin, tissue-type urokinase-type plasminogen (tPA, uPA), affect the fate PAI-1. Here, we measured changes in solvent accessibility dynamics an unresolved functional region, reactive center loop (RCL), upon binding these ligands. Binding catalytically inactive S195A variant tPA to RCL causes increase fluorescence, indicating greater protection, at C-terminus, while mobility along remains relatively unchanged. In contrast, fluorescence large decrease N-terminal observed S195A-uPA At site distant from RCL, vitronectin results modest proximal end without restricting overall dynamics. These provide new evidence ligand effects on conformation differences Michaelis complex activators that can be used development more specific inhibitors This study also first use electron paramagnetic resonance (EPR) spectroscopy investigate PAI-1 SIGNIFICANCE Balanced blood homeostasis controlled cell migration requires coordination between proteases, serpins, cofactors. ligands form noncovalent complexes, which influence outcome inhibition physiological processes. reveals via within complexes exploited develop drugs treatment diseases unbalanced serpin activity.