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The structure of a serpin–protease complex revealed by intramolecular distance measurements using donor–donor energy migration and mapping of interaction sites
Umeå University, Faculty of Medicine, Medical Biochemistry and Biophsyics.
Faculty of Science and Technology, Chemistry.
Umeå University, Faculty of Medicine, Medical Biochemistry and Biophsyics.
Umeå University, Faculty of Medicine, Medical Biochemistry and Biophsyics.
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2000 (English)In: Structure, Vol. 8, no 4, 397-405 p.Article in journal (Refereed) Published
Abstract [en]

Background: The inhibitors that belong to the serpin family are widely distributed regulatory molecules that include most protease inhibitors found in blood. It is generally thought that serpin inhibition involves reactive-centre cleavage, loop insertion and protease translocation, but different models of the serpin–protease complex have been proposed. In the absence of a spatial structure of a serpin–protease complex, a detailed understanding of serpin inhibition and the character of the virtually irreversible complex have remained controversial.

Results: We used a recently developed method for making precise distance measurements, based on donor–donor energy migration (DDEM), to accurately triangulate the position of the protease urokinase-type plasminogen activator (uPA) in complex with the serpin plasminogen activator inhibitor type 1 (PAI-1). The distances from residue 344 (P3) in the reactive-centre loop of PAI-1 to residues 185, 266, 313 and 347 (P1′) were determined. Modelling of the complex using this distance information unequivocally placed residue 344 in a position at the distal end from the initial docking site with the reactive-centre loop fully inserted into β sheet A. To validate the model, seven single cysteine substitution mutants of PAI-1 were used to map sites of protease–inhibitor interaction by fluorescence depolarisation measurements of fluorophores attached to these residues and cross-linking using a sulphydryl-specific cross-linker.

Conclusions: The data clearly demonstrate that serpin inhibition involves reactive-centre cleavage followed by full-loop insertion whereby the covalently linked protease is translocated from one pole of the inhibitor to the opposite one.

Place, publisher, year, edition, pages
2000. Vol. 8, no 4, 397-405 p.
Keyword [en]
Cross-linking, Donor–donor energy migration, Fluorescence, Intramolecular distance, PAI-1, serpin
URN: urn:nbn:se:umu:diva-8572DOI: doi:10.1016/S0969-2126(00)00121-0OAI: diva2:148243
Available from: 2008-01-29 Created: 2008-01-29 Last updated: 2011-01-14Bibliographically approved

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Wilczynska, MalgorzataJohansson, Lennart B-ÅNy, Tor
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