Functional assays of megsin. (a) SDS-PAGE under a nonreduced condition, followed by CBB staining (left and middle panels) or immunoblotting using anti–t-PA antibody (right panel), revealed functional binding of megsin to plasmin, but not to other serine proteases such as t-PA and thrombin. Lane 1, plasmin; lane 2, antiplasmin; lane 3, plasmin plus antiplasmin; lane 4, megsin; lane 5, plasmin plus megsin; lane 6, thrombin; lane 7, antithrombin; lane 8, thrombin plus antithrombin; lane 9, megsin; lane 10, thrombin plus megsin; lane 11, t-PA; lane 12, PAI-1; lane 13, t-PA plus PAI-1; lane 14, megsin; lane 15, t-PA plus megsin. The complex of serine protease and serpin is indicated by asterisks. (b) The inhibitory effect of megsin to plasmin activity. Diamonds, substrate alone; open squares, plasmin; filled squares, plasmin and antiplasmin (1:2); open circles, plasmin and megsin (1:10); filled circles, plasmin and inactivated megsin (1:10); open triangles, ovalbumin; filled triangles, albumin.