Non-toxic type 2 RIP which strongly inhibits mammalian protein synthesis but does not affect plant nor bacterial protein synthesis. The A chain is responsible for inhibiting protein synthesis through the catalytic inactivation of 60S ribosomal subunits by removing adenine from position 4,324 of 28S rRNA. The B chain is a galactose-specific lectin that facilitates the binding of nigrin b to the cell membrane that precedes endocytosis. Endohydrolysis of the N-glycosidic bond at one specific adenosine on the 28S rRNA. Disulfide-linked dimer of A and B chains. In the N-terminal section; belongs to the ribosome-inactivating protein family. Type 2 RIP subfamily.