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 binds to cell receptors and probably facilitates the entry into the cell of the A chain; B chains are also responsible for cell agglutination (lectin activity). Endohydrolysis of the N-glycosidic bond at one specific adenosine on the 28S rRNA. Disulfide-linked dimer of A and B chains. Several isoforms exist. Belongs to the ribosome-inactivating protein family. Type 2 RIP subfamily.