BACKGROUND: Plasminogen activator inhibitor type 1 (PAI-1) is an important endogenous regulator of the fibrinolytic system. Reduction of PAI-1 activity has been shown to enhance dissolution of blood clots. Like other serpins, PAI-1 binds covalently to a target serine protease, thereby irreversibly inactivating the enzyme. During this process the exposed reactive-centre loop of PAI-1 is believed to undergo a conformational change becoming inserted into beta sheet A of the serpin. Incubation with peptides from the reactive-centre loop transform serpins into a substrate for their target protease. It has been hypothesised that these peptides bind to beta sheet A, thereby hindering the conformational rearrangement leading to loop insertion and formation of the stable serpin-protease complex. RESULTS: We report here the 1.95 A X-ray crystal structure of a complex of a glycosylated mutant of PAI-1, PAI-1-ala335Glu, with two molecules of the inhibitory reactive-centre loop peptide N-Ac-TVASS-NH2. Both bound peptide molecules are located between beta strands 3A and 5A of the serpin. The binding kinetics of the peptide inhibitor to immobilised PAI-1-Ala335Glu, as monitored by surface plasmon resonance, is consistent with there being two different binding sites. CONCLUSIONS: This is the first reported crystal structure of a complex formed between a serpin and a serpin inhibitor. The localisation of the inhibitory peptide in the complex strongly supports the theory that molecules binding in the space between beta strands 3A and 5A of a serpin are able to prevent insertion of the reactive-centre loop into beta sheet A, thereby abolishing the ability of the serpin to irreversibly inactivate its target enzyme. The characterisation of the two binding sites for the peptide inhibitor provides a solid foundation for computer-aided design of novel, low molecular weight PAI-1 inhibitors.
BACKGROUND:Plasminogen activator inhibitor type 1 (PAI-1) is an important endogenous regulator of the fibrinolytic system. Reduction of PAI-1 activity has been shown to enhance dissolution of blood clots. Like other serpins, PAI-1 binds covalently to a target serine protease, thereby irreversibly inactivating the enzyme. During this process the exposed reactive-centre loop of PAI-1 is believed to undergo a conformational change becoming inserted into beta sheet A of the serpin. Incubation with peptides from the reactive-centre loop transform serpins into a substrate for their target protease. It has been hypothesised that these peptides bind to beta sheet A, thereby hindering the conformational rearrangement leading to loop insertion and formation of the stable serpin-protease complex. RESULTS: We report here the 1.95 A X-ray crystal structure of a complex of a glycosylated mutant of PAI-1, PAI-1-ala335Glu, with two molecules of the inhibitory reactive-centre loop peptide N-Ac-TVASS-NH2. Both bound peptide molecules are located between beta strands 3A and 5A of the serpin. The binding kinetics of the peptide inhibitor to immobilised PAI-1-Ala335Glu, as monitored by surface plasmon resonance, is consistent with there being two different binding sites. CONCLUSIONS: This is the first reported crystal structure of a complex formed between a serpin and a serpin inhibitor. The localisation of the inhibitory peptide in the complex strongly supports the theory that molecules binding in the space between beta strands 3A and 5A of a serpin are able to prevent insertion of the reactive-centre loop into beta sheet A, thereby abolishing the ability of the serpin to irreversibly inactivate its target enzyme. The characterisation of the two binding sites for the peptide inhibitor provides a solid foundation for computer-aided design of novel, low molecular weight PAI-1 inhibitors.
Authors: Ashley A Reinke; Shih-Hon Li; Mark Warnock; Maxim E Shaydakov; Naga Sandhya Guntaka; Enming J Su; Jose A Diaz; Cory D Emal; Daniel A Lawrence Journal: J Biol Chem Date: 2018-12-03 Impact factor: 5.157
Authors: Lawrence C Thompson; Sumit Goswami; David S Ginsberg; Duane E Day; Ingrid M Verhamme; Cynthia B Peterson Journal: Protein Sci Date: 2011-02 Impact factor: 6.725
Authors: Giorgia Cazzolli; Fang Wang; Silvio a Beccara; Anne Gershenson; Pietro Faccioli; Patrick L Wintrode Journal: Proc Natl Acad Sci U S A Date: 2014-10-13 Impact factor: 11.205
Authors: Zhonghui Lin; Longguang Jiang; Cai Yuan; Jan K Jensen; Xu Zhang; Zhipu Luo; Barbara C Furie; Bruce Furie; Peter A Andreasen; Mingdong Huang Journal: J Biol Chem Date: 2011-01-03 Impact factor: 5.157
Authors: Shih-Hon Li; Ashley A Reinke; Karen L Sanders; Cory D Emal; James C Whisstock; Jeanne A Stuckey; Daniel A Lawrence Journal: Proc Natl Acad Sci U S A Date: 2013-12-02 Impact factor: 11.205
Authors: Katrine E Pedersen; Anja P Einholm; Anni Christensen; Lotte Schack; Troels Wind; John M Kenney; Peter A Andreasen Journal: Biochem J Date: 2003-06-15 Impact factor: 3.857