Galactose plant toxin binding

Various plant toxins, mostly ribosome-inactivating proteins (RIPs), have been identified that bind to any mammalian cell surface expressing galactose units and are subsequently internalized by RME (67). Toxins such as nigrin b (68), a-sarcin (69), ricin and saporin (70), viscumin (71), and modeccin (72) are highly toxic upon oral administration (i.e., are rapidly internalized). The possibility exists, therefore, that modified and, most important, less toxic subunits of these compound can be used to facilitate the uptake of macro-molecular compounds or microparticulates. 

Abrin- and ricin-resistant variants of established HeLa cell lines have been characterized. The reduced number of binding sites on two of the cell variants is due to an increased level of neuraminic acid on oligosaccharide chains terminated at the non-reducing end by D-galactose. However, these over-sialylated variants are not cross-resistant to another plant toxin, modeccin,... 

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