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It has been reported that Clostridium botulinum type C 16S progenitor toxin
(C16S toxin) first binds to the sialic acid on the cell surface of mucin before
invading cells [A. Nishikawa, N. Uotsu, H. Arimitsu, J.C. Lee, Y. Miura, Y.
Fujinaga, H. Nakada, T. Watanabe, T. Ohyama, Y. Sakano, K. Oguma, The receptor
and transporter for internalization of Clostridium botulinum type C progenitor
toxin into HT-29 cells, Biochem. Biophys. Res. Commun. 319 (2004) 327-333]. In
this study we investigated the binding properties of the C16S toxin to
glycoproteins. Although the toxin bound to membrane blotted mucin derived from
the bovine submaxillary gland (BSM), which contains a lot of sialyl
oligosaccharides, it did not bind to neuraminidase-treated BSM. The binding of
the toxin to BSM was inhibited by N-acetylneuraminic acid, N-glycolylneuraminic
acid, and sialyl oligosaccharides strongly, but was not inhibited by neutral
oligosaccharides. Both sialyl alpha2-3 lactose and sialyl alpha2-6 lactose
prevented binding similarly. On the other hand, the toxin also bound well to
porcine gastric mucin. In this case, neutral oligosaccharides might play an
important role as ligand, since galactose and lactose inhibited binding. These
results suggest that the toxin is capable of recognizing a wide variety of
oligosaccharide structures.
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