Structural and enzymatic properties of an in vivo proteolytic form of PD-S2, type 1 ribosome-inactivating protein from seeds of Phytolacca dioica L

PD-S2, type 1 ribosome-inactivating protein from Phytolacca dioica L seeds, is an N-beta-glycosidase likely involved in plant defence. In this work, we purified and characterized an in vivo proteolytic form of PD-S2, named cutPD-S2. Spectroscopic characterization of cutPD-S2 showed that the proteolytic cleavage between Asn195 and Arg196 does not alter the protein fold, but significantly affects its thermal stability. Most importantly, the proteolytic cleavage induces a 370-fold decrease of PD-S2 capacity of inhibiting in vitro protein biosynthesis.