– Thionins are small plant proteins which are toxic to animal cells. They seem to exert their toxic effect at the level of the cell membrane. Their precise function is not known. Viscotoxin-A3 Protein, Viscum album, Recombinant (His) is expressed in yeast with N-6xHis tag. The predicted molecular weight is 6.8 kDa and the accession number is P01538.