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 abrin 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. The B chain is composed of two domains, each domain consists of 3 homologous subdomains (alpha, beta, gamma). In the N-terminal section; belongs to the ribosome-inactivating protein family. Type 2 RIP subfamily.