PDBsum entry 1a7c

Hydrolase inhibitor/peptide

PDB id: 1a7c

Contents

Protein chain

364 a.a. *

Ligands

ACE-THR-VAL-ALA-SER-SER-NH2 ×2

NAG-NAG-RIP

NAG

Waters ×69

* Residue conservation analysis

PDB id:

1a7c

Name:

Hydrolase inhibitor/peptide

Title:

Human plasminogen activator inhibitor type-1 in complex with a pentapeptide

Structure:

Plasminogen activator inhibitor type 1. Chain: a. Synonym: pai-1. Engineered: yes. Mutation: yes. Pentapeptide. Chain: b, c. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Expressed in: cricetulus griseus. Expression_system_taxid: 10029. Expression_system_cell_line: cho. Synthetic: yes

Biol. unit:

Trimer (from PQS)

Resolution:

1.95Å R-factor: 0.181 R-free: 0.210

Authors:

Y.Xue,T.Inghardt,L.Sjolin,J.Deinum

Key ref:

Y.Xue et al. (1998). Interfering with the inhibitory mechanism of serpins: crystal structure of a complex formed between cleaved plasminogen activator inhibitor type 1 and a reactive-centre loop peptide. Structure, 6, 627-636. PubMed id: 9634700 DOI: 10.1016/S0969-2126(98)00064-1

Date:

12-Mar-98 Release date: 23-Mar-99

Protein chain

P05121  (PAI1_HUMAN) -  Plasminogen activator inhibitor 1 from Homo sapiens

Seq: 402 a.a.

Struc: 364 a.a.

DOI no: 10.1016/S0969-2126(98)00064-1

Structure 6:627-636 (1998)

PubMed id: 9634700

Interfering with the inhibitory mechanism of serpins: crystal structure of a complex formed between cleaved plasminogen activator inhibitor type 1 and a reactive-centre loop peptide.

Y.Xue, P.Björquist, T.Inghardt, M.Linschoten, D.Musil, L.Sjölin, J.Deinum.

ABSTRACT

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.

Selected figure(s)

Figure 1.
Figure 1. The structures of latent and active PAI-1. (a) Schematic model of latent PAI-1 [17] and (b) a constructed model of active PAI-1 [16] based on the structures of both latent PAI-1 and antithrombin III [38] with some important structural domains indicated. The protein is shown from the front with the b sheet A coloured red; b strands 3A to 5A are indicated. (The figure was prepared using the program MOLSCRIPT [39].)

The above figure is reprinted by permission from Cell Press: Structure (1998, 6, 627-636) copyright 1998.

Figure was selected by an automated process.