Cleavage of recombinant proteins by normal plasma. The recombinant substrates (I-V) were incubated with normal plasma at 37°C for 0 hours (lanes 1, 3, 5, 7, and 9) or 1 hour (lanes 2, 4, 6, 8, and 10). Both substrates and products were detected by Western blot using anti-GST. The product bands including N-terminal GST-tag are indicated by arrowheads. Substrates III and IV were cleaved more efficiently than I and II, and substrate V was not cleaved. The arrowed bands observed in all lanes are nonspecific signals derived from plasma albumin. The bands with asterisks, probably contaminating degradation products, are reproducible background signals.