Possesses antiviral potency. Inhibits viral infection of plants (tobacco mosaic virus) (PubMed:10403789). Inhibits protein synthesis (PubMed:2930487, PubMed:6091760, PubMed:2248976, PubMed:10403789, PubMed:10595542). Releases both adenine and guanine from Escherichia coli rRNA in vitro. Activity on guanine is 20 times slower than that on adenine (PubMed:10595542). Endohydrolysis of the N-glycosidic bond at one specific adenosine on the 28S rRNA. Monomer. Expressed in spring leaves (at protein level) (PubMed:10403789, PubMed:10595542). Expressed in roots (at protein level) (PubMed:2248976). LD(50) is 1.89 mg/kg by intraperitoneal injection into mice (at 48 hours post-injection). LD(50) is 0.95 mg/kg by intraperitoneal injection into mice (at 14 days post-injection). Depurinates genomic RNA of immunodeficiency virus type-I (HIV-I) and bacteriophage (MS 2) RNA. Inhibits the replication of HIV-1 in human peripheral blood mononuclear cells with IC(50) value of 14 nM. Belongs to the ribosome-inactivating protein family. Type 1 RIP subfamily.