Comparison of the binding characteristics of two different preparations of tetanus toxin to rat brain membranes.
Two different preparations of tetanus toxin (HTT and WTT) were iodinated, and their binding to rat brain membranes characterized. Under optimal binding conditions (25 mM Tris-acetate, pH 6.0), both preparations bound to a large number of high affinity sites, thought to be gangliosides. Binding constants were identical. However, in a physiological buffer (Krebs-Ringer, pH 7.4) binding of the two toxin preparations showed a number of differences. Under these conditions we have previously shown that HTT binding is markedly reduced, and that there are two classes of sites, a small number of heat-, sialidase- and protease-sensitive high affinity sites, and a larger number of sialidase-sensitive, heat- and protease-resistant lower affinity sites, probably gangliosides (PIERCE et al. (1986) Biochem. J. 236, 845-852). Although WTT bound to these same two sites, it displayed a higher affinity for the protease-resistant site than did HTT. WTT also bound to free or immobilized trisialoganglioside with higher affinity than HTT, consistent with the view that the protease-resistant site represents binding to ganglioside. In contrast, both toxin preparations bound to the protease-sensitive site with similar affinities. These observations may explain the four to five-fold higher levels of WTT binding to brain membranes, and the fact that a smaller percentage of total WTT binding is protease sensitive. Despite their different ganglioside-binding properties, both toxin preparations showed comparable neurotoxic activities, and appeared identical on SDS gels.
Parton
R G
RG
Department of Biochemistry, University of Leicester, U.K.
Davison
M D
MD
Critchley
D R
DR
D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects*; D005732:Gangliosides / Q000494:pharmacology; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D008566:Membranes / Q000378:metabolism; D009498:Neurotoxins / Q000633:toxicity; D051381:Rats; D011919:Rats, Inbred Strains; D013744:Tetanus Toxin / Q000378:metabolism*
D005732:Gangliosides; D007457:Iodine Radioisotopes; D009498:Neurotoxins; D013744:Tetanus Toxin; C016806:trisialoganglioside