Structure-based sequence alignment for the beta-trefoil subdomain of the clostridial neurotoxin family provides residue level information about the putative ganglioside binding site

Clostridial neurotoxins embrace a family of extremely potent toxins compris ed of tetanus toxin (TeNT) and seven different serotypes of botulinum toxin (BoNT/A-G). The beta-trefoil subdomain of the C-terminal part of the heavy chain (Hc), responsible for ganglioside binding, is the most divergent reg ion in clostridial neurotoxins with sequence identity as low as 15%, We re- examined the alignment between family sequences within this subdomain, sinc e in this region all alignments published to date show obvious inconsistenc ies with the beta-trefoil fold, The final alignment was obtained by conside ring the general constraints imposed by this fold, and homology modeling st udies based on the TeNT structure, Recently solved structures of BoNT/A con firm the validity of this structure-based approach. Taking into account bio chemical data and crystal structures of TeNT and BoNT/A, we also re-examine d the location of the putative ganglioside binding site and, using the new alignment, characterized this site in other BoNT serotypes, (C) 2000 Federa tion of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.