A triple mutation on the wild-type background makes this Human PAI-1 selectively inhibit tPA. Urokinase inhibition is limited to 1/25,000 of tPA inhibition by the P3Tyr-P2Ser-P1Tyr mutation.

References:
Sherman PM. et al. (1995) J Biol Chem 270:9301-9306.
Gene Name: SERPINE1
Gene ID: 5054
Swiss-Prot/UniProt ID: P05121