Identification of a Binding Site for Ganglioside on the Receptor Binding Domain of Tetanus Toxin

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• 作者：Heather A. Louch ; Ellen S. Buczko ; Mary A. Woody ; Richard M. Venable ; and Willie F. Vann
• 刊名：Biochemistry
• 出版年：2002
• 出版时间：November 19, 2002
• 年：2002
• 卷：41
• 期：46
• 页码：13644 - 13652
• 全文大小：532K
• 年卷期：v.41,no.46(November 19, 2002)
• ISSN：1520-4995

文摘

The carboxyl-terminal region of the tetanus toxin heavy chain (H_C fragment) binds to di- andtrisialylgangliosides on neuronal cell membranes. To determine which amino acids in tetanus toxin areinvolved in ganglioside binding, homology modeling was performed using recently resolved X-raycrystallographic structures of the tetanus toxin H_C fragment. On the basis of these analyses, two regionsin tetanus toxin that are structurally homologous with the binding domains of other sialic acid and galactose-binding proteins were targeted for mutagenesis. Specific amino acids within these regions were alteredusing site-directed mutagenesis. The amino acid residue tryptophan 1288 was found to be critical forbinding of the H_C fragment to ganglioside GT1b. Docking of GD1b within this region of the toxin suggestedthat histidine 1270 and aspartate 1221 were within hydrogen bonding distance of the ganglioside. Thesetwo residues were mutagenized and found also to be important for the binding of the tetanus toxin H_Cfragment to ganglioside GT1b. In addition, the H_C fragments mutagenized at these residues have reducedlevels of binding to neurites of differentiated PC-12 cells. These studies indicate that the amino acidstryptophan 1288, histidine 1270, and aspartate 1221 are components of the GT1b binding site on thetetanus toxin H_C fragment.