.... The last protease in this sequence is encoded by easter , which is a candidate to activate proteolytically the ligand encoded by spätzle . Here, we demonstrate biochemically that the zymogen form of Easter is processed in vivo by a proteolytic cleavage event that requires the three upstream proteases...

... in the unprocessed zymogen form and appears to be evenly distributed in the extracellular space, indicating that the asymmetric activity of wildtype easter must arise post-translationally. A dominant mutant form of easter that does not require cleavage of the zymogen for activity (ea ▵N) is active both dorsally...