Interactions of plasminogen activator inhibitor-1 with vitronectin involve an extensive binding surface and induce mutual conformational rearrangements

TY - JOUR

T1 - Interactions of plasminogen activator inhibitor-1 with vitronectin involve an extensive binding surface and induce mutual conformational rearrangements

AU - Blouse, Grant E

AU - Dupont, Daniel Miotto

AU - Schar, Christine R

AU - Jensen, Jan K

AU - Minor, Kenneth H

AU - Anagli, John Y

AU - Gårdsvoll, Henrik

AU - Ploug, Michael

AU - Peterson, Cynthia B

AU - Andreasen, Peter A

PY - 2009/3/3

Y1 - 2009/3/3

N2 - In order to explore early events during the association of plasminogen activator inhibitor-1 (PAI-1) with its cofactor vitronectin, we have applied a robust strategy that combines protein engineering, fluorescence spectroscopy, and rapid reaction kinetics. Fluorescence stopped-flow experiments designed to monitor the rapid association of PAI-1 with vitronectin indicate a fast, concentration-dependent, biphasic binding of PAI-1 to native vitronectin but only a monophasic association with the somatomedin B (SMB) domain, suggesting that multiple phases of the binding interaction occur only when full-length vitronectin is present. Nonetheless, in all cases, the initial fast interaction is followed by slower fluorescence changes attributed to a conformational change in PAI-1. Complementary experiments using an engineered, fluorescently silent PAI-1 with non-natural amino acids showed that concomitant structural changes occur as well in native vitronectin. Furthermore, we have measured the effect of vitronectin on the rate of insertion of the reactive center loop into beta-sheet A of PAI-1 during reaction with target proteases. With a variety of PAI-1 variants, we observe that both full-length vitronectin and the SMB domain have protease-specific effects on the rate of loop insertion but that the two exhibit clearly different effects. These results support a model for PAI-1 binding to vitronectin in which the interaction surface extends beyond the region of PAI-1 occupied by the SMB domain. In support of this model are recent results that define a PAI-1-binding site on vitronectin that lies outside the somatomedin B domain (Schar, C. R., Blouse, G. E., Minor, K. H., and Peterson, C. B. (2008) J. Biol. Chem. 283, 10297-10309) and the complementary site on PAI-1 (Schar, C. R., Jensen, J. K., Christensen, A., Blouse, G. E., Andreasen, P. A., and Peterson, C. B. (2008) J. Biol. Chem. 283, 28487-28496).

AB - In order to explore early events during the association of plasminogen activator inhibitor-1 (PAI-1) with its cofactor vitronectin, we have applied a robust strategy that combines protein engineering, fluorescence spectroscopy, and rapid reaction kinetics. Fluorescence stopped-flow experiments designed to monitor the rapid association of PAI-1 with vitronectin indicate a fast, concentration-dependent, biphasic binding of PAI-1 to native vitronectin but only a monophasic association with the somatomedin B (SMB) domain, suggesting that multiple phases of the binding interaction occur only when full-length vitronectin is present. Nonetheless, in all cases, the initial fast interaction is followed by slower fluorescence changes attributed to a conformational change in PAI-1. Complementary experiments using an engineered, fluorescently silent PAI-1 with non-natural amino acids showed that concomitant structural changes occur as well in native vitronectin. Furthermore, we have measured the effect of vitronectin on the rate of insertion of the reactive center loop into beta-sheet A of PAI-1 during reaction with target proteases. With a variety of PAI-1 variants, we observe that both full-length vitronectin and the SMB domain have protease-specific effects on the rate of loop insertion but that the two exhibit clearly different effects. These results support a model for PAI-1 binding to vitronectin in which the interaction surface extends beyond the region of PAI-1 occupied by the SMB domain. In support of this model are recent results that define a PAI-1-binding site on vitronectin that lies outside the somatomedin B domain (Schar, C. R., Blouse, G. E., Minor, K. H., and Peterson, C. B. (2008) J. Biol. Chem. 283, 10297-10309) and the complementary site on PAI-1 (Schar, C. R., Jensen, J. K., Christensen, A., Blouse, G. E., Andreasen, P. A., and Peterson, C. B. (2008) J. Biol. Chem. 283, 28487-28496).

KW - Binding Sites

KW - Fluorescence

KW - Fluorescent Dyes

KW - Humans

KW - Kinetics

KW - Models, Molecular

KW - Peptide Hydrolases

KW - Plasminogen Activator Inhibitor 1

KW - Protein Binding

KW - Protein Structure, Secondary

KW - Protein Structure, Tertiary

KW - Surface Properties

KW - Tryptophan

KW - Vitronectin

KW - Journal Article

KW - Research Support, N.I.H., Extramural

KW - Research Support, Non-U.S. Gov't

U2 - 10.1021/bi8017015

DO - 10.1021/bi8017015

M3 - Journal article

C2 - 19193026

SN - 0006-2960

VL - 48

SP - 1723

EP - 1735

JO - Biochemistry

JF - Biochemistry

IS - 8

ER -