Serpin-resistant mutants of human tissue-type plasminogen activator

Edwin L. Madison, Elizabeth J. Goldsmith, Robert D. Gerard, Mary Jane H Gething, Joseph F. Sambrook

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Abstract

TISSUE-type plasminogen activator (t-PA) converts the inactive zymogen, plasminogen, into the powerful protease, plasmin, which then degrades the fibrin meshwork of thrombi1-3. To prevent systemic activation of plasminogen, plasma contains several inhibitors of t-PA, the most important of which is plasminogen activator inhibitor-1 (PAI-1), a member of the serpin superfamily4-6. As the ability to produce serpin-resistant variants of t-PA could increase the potential of this enzyme as a thrombolytic agent, we have used the known three-dimensional structure of the complex between trypsin and bovine pancreatic trypsin inhibitor (BPTI) to model the interactions between the active site of human t-PA and PAI-1. On the basis of this model we then altered by site-directed mutagenesis those amino acids of t-PA predicted to make contact with PAI-1 but not with the substrate plasminogen. We report here that although the resulting mutants have enzymatic properties similar to those of wild-type t-PA, they display significant resistance to inhibition by PAI-1. For example, following incubation with an amount of the serpin that completely inhibits the wild-type enzyme, one variant retains 95% of its initial activity. This mutant is also resistant to inhibition by the complex mixture of serpins present in human plasma.

Original languageEnglish (US)
Pages (from-to)721-724
Number of pages4
JournalNature
Volume339
Issue number6227
DOIs
StatePublished - Jan 1 1989

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Madison, E. L., Goldsmith, E. J., Gerard, R. D., Gething, M. J. H., & Sambrook, J. F. (1989). Serpin-resistant mutants of human tissue-type plasminogen activator. Nature, 339(6227), 721-724. https://doi.org/10.1038/339721a0