Galbeta1-3GalNAcbeta1-4Galbeta1-4Glc oligosaccharide-binding lectin. Binds strongly to the oligosaccharides of ganglioside GM1b and to a lesser extent its precursor asialo-GM1 (PubMed:31769916, PubMed:33328520). Binds weakly to asialo-GM2 oligosaccharide and to the glycan moiety of globo-series stage-specific embryonal antigen 4 (SSEA-4) hexaose (PubMed:31769916). Binds galactose, N-acetylgalactose and lactose. Does not bind GM1 (PubMed:33328520). Does not bind to Gal-beta1,3-GalNAc (Thomsen-Friedenreich antigen), the oligosaccharide of GM1a ganglioside or SSEA-4 tetraose. Does not bind to N-glycans, O-glycans or glycosaminoglycans of glycoproteins. Does not bind Lewis glycans, derivatives of lactose or N-acetyllactosamine or blood group (ABH-type) oligosaccharides (PubMed:31769916). Does not bind glucose (PubMed:33328520). Has hemagglutination activity towards rabbit erythrocytes (PubMed:31769916, PubMed:33328520). Displays cytotoxic effects against various cultured cell lines including human breast (MCF7), cervical (HeLa) and colon cancer (Caco2) cell lines, as well as dog kidney (MDCK) cell line that express asialo-GM1 oligosaccharide at their cell surface. Shows dose- and time-dependent activation of MKK3/6, ERK1/2 and p38 MAPK, as well as caspase-3/9 in HeLa cervical cancer cells. No cytotoxic effect on BT474 human breast cancer cell line. May be involved in recognition of glycans found on parasitic or symbiotic microorganisms (PubMed:31769916). Hemagglutination activity requires divalent cations such as Ca(2+) (PubMed:31769916, PubMed:33328520). Hemagglutination activity is weakly inhibited by monosaccharides such as D-Gal (25 mM), D-GalNAc (25 mM) and D-Fuc (25 mM) and by disaccharides such as melibiose (25 mM) and lactose (25 mM). Hemagglutination activity is inhibited by bovine submaxillary mucin, but not by porcine stomach mucin or fetuin (PubMed:31769916). Homodimer. Highest expression in the outer part of the mantle rim. Highly expressed in gills, with a much lower expression in the digestive gland and posterior adductor muscle. Scarcely detectable in foot. This protein has potential for the detection and control of certain cancer cells and cells of the immune system, that display asialo-GM1 (PubMed:33328520). Has potential clinical applications since it recognizes glycans expressed specifically by the target antigen for Guillain-Barre syndrome (GM1b), natural killer (NK) cells and basophils (asialo-GM1) and glioblastoma multiforme (SSEA-4) in vertebrates (PubMed:31769916).