Fig. 3.

Activation of Plg with uPa reveals a novel step-wise processing.A, monitoring by native mass spectrometry, the species formed following the addition of uPa to Plg (at a ratio of 1:250) reveals a step-wise N-terminal cleavage, starting with the release of Glu1–Arg67, followed by Met68–Lys77. The canonical Lys-Plm product is formed only later in time, when compared with the product that released Glu1–Arg67. B, annotated proteoform profile of all species, including Plg, the novel intermediate and Lys-Plm. C, schematic of the stepwise activation of Plg. Plg, plasminogen; uPa, urokinase plasminogen activator.