ADP-riboxanase effector that mediates arginine ADP-riboxanation of host target protein(s) (PubMed:34671164). Does not catalyze ADP-riboxanation of host CASP4/CASP11 (PubMed:34671164). L-arginyl-[protein] + NAD(+) = ADP-riboxanated L-argininyl-[protein] + H(+) + NH4(+) + nicotinamide Secreted via the type III secretion system (TTSS). Belongs to the OspC family.