title: Structural bases of the redox-dependent conformational switch in the serpin PAI-2.
abstract: Depending on the redox-status, the serpin plasminogen activator inhibitor type 2 (PAI-2) can exist in either a stable monomeric or polymerogenic form. The latter form, which spontaneously forms loop-sheet polymers, has an open beta-sheet A and is stabilized by a disulfide bond between C79 (in the CD-loop) and C161 (at the bottom of PAI-2). Reduction of this bond results in a closing of the beta-sheet A and converts PAI-2 to a stable monomeric form. Here we show that the stable monomeric and polymerogenic forms of PAI-2 are fully interconvertible, depending on redox-status of the environment. Our intramolecular distance measurements indicate that the CD-loop folds mainly on one side of the stable monomeric form of the inhibitor. However, the loop can translocate about 54A to the bottom of PAI-2 so that the C79-C161 disulfide bond can form under oxidizing conditions. We show also that the redox-active C79 can form a disulfide-link to the matrix protein vitronectin, suggesting that vitronectin can stabilize active PAI-2 in extracellular compartments. PAI-2 is therefore a rare example of a redox-sensitive protein for which the activity and polymerization ability are regulated by reversible disulfide bond formation leading to major translocation of a loop and significant conformational changes in the molecule.
authors.affiliation: Department of Medical Biochemistry and Biophysics, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Sergei
authors.initials: S
authors.lastname: Lobov
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Wilczynska
authors.forename: Fredrik
authors.initials: F
authors.lastname: Bergström
authors.forename: Lennart B-A
authors.initials: LB
authors.lastname: Johansson
authors.forename: Tor
authors.initials: T
authors.lastname: Ny
mesh_terms: D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D004220:Disulfides / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction; D017396:Plasminogen Activator Inhibitor 2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018583:Pliability; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D019096:Vitronectin / Q000737:chemistry / Q000378:metabolism
chemical_list: D004220:Disulfides; D017396:Plasminogen Activator Inhibitor 2; D019096:Vitronectin; D003545:Cysteine