Thrombin-variable region 1 (VR1). Evidence for the dominant contribution of VR1 of serine proteases to their interaction with plasminogen activator inhibitor 1.

A.J Horrevoets,G Tans,A.E Smilde,A.J Van Zonneveld,H Pannekoek

doi:10.1016/s0021-9258(18)54001-1

A.J Horrevoets, G Tans + Show 3 more

Open Access

https://doi.org/10.1016/s0021-9258(18)54001-1

Copy DOI

Abstract

The importance of a specific variable region in different serine proteases for the interaction with plasminogen activator inhibitor 1 (PAI-1) is studied. To that end, we have constructed a thrombin substitution variant, thrombin-VR1, in which the entire variable region 1 (VR1) of the protease domain (Phe-34 to Leu-40) has been replaced by the corresponding sequence (Phe-294 to Phe-305) of tissue-type plasminogen activator. The substitution resulted in a 2000-fold increase of the second-order rate constant of inhibition by PAI-1 (k2 = 2.2 x 10(6) M-1 s-1) as compared to alpha-thrombin (k2 = 1.1 x 10(3) M-1 s-1). Inhibition of thrombin-VR1 by PAI-1 is mediated by the formation of SDS-stable, enzyme-inhibitor complexes. The substitution did not affect the rate constant of inhibition by antithrombin III, whereas clotting efficiency and the rate of inhibition by heparin cofactor II were decreased 3-fold. These results demonstrate the importance and specificity of the protease domain VR1 region for the interaction of PAI-1 with its target proteases.

Highlights

From the Department of Molecular Biology, Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, 1066 CX Amsterdam, The Netherlands
This paper provides positive evidence for the dominant role of the variable region 1 (VR1) region of serine proteases in thespecific interaction with plasminogen activator inhibitor 1 (PAI-1)
Using the Recombinant Vaccinia Virus ExpressionSystem-Properformed on 7.5% (w/v) polyacrylamide gels (19), and the radiolathrombinandprothrombin-VR1 were expressed in a recombinant beled material was visualized by autoradiography

Summary

CCA AGG

The replacement of the amino~acidsequence RKSfiNEL (prothrombin residues 340-346) by AKHRRSPGERF (&PAresidues 295-305). The mutated fragment was used to substitute the “wild-type” SstI-EglII. Role of Protease-VRl Domain in Inhibition by PAI-1 fragment of prothrombin in pcDNA. The absence of undesired mu- ple buffer (5% (w/v) SDS, 45% (v/v) glycerol, 0.05 M Tris-HC1 Expression and Partial Purification of Recombinant Prothrombin were briefly heated a t 95 "Cto quench the reaction. Using the Recombinant Vaccinia Virus ExpressionSystem-Properformed on 7.5% (w/v) polyacrylamide gels (19), and the radiolathrombinandprothrombin-VR1 were expressed in a recombinant beled material was visualized by autoradiography. Vaccinia virus expression system, essentially asdescribed before (14). Prothrombin cDNAwas inserted as an EcoRI-XbaI fragment into the vaccinia expression vector pATA-18, and thymidine kinase-neg-

RESULTS

PWQVML FAKHRRSPGERF LCGA

Findings

DISCUSSION