– 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). Inhibits growth of the human tumor cell line Molt4. Viscumin Protein, Viscum album, Recombinant (His) is expressed in yeast with N-6xHis tag. The predicted molecular weight is 30.4 kDa and the accession number is P81446.