title: Sequence homology and structural analysis of the clostridial neurotoxins.
abstract: The clostridial neurotoxins (CNTs), comprised of tetanus neurotoxin (TeNT) and the seven serotypes of botulinum neurotoxin (BoNT A-G), specifically bind to neuronal cells and disrupt neurotransmitter release by cleaving proteins involved in synaptic vesicle membrane fusion. In this study, multiple CNT sequences were analyzed within the context of the 1277 residue BoNT/A crystal structure to gain insight into the events of binding, pore formation, translocation, and catalysis that are required for toxicity. A comparison of the TeNT-binding domain structure to that of BoNT/A reveals striking differences in their surface properties. Further, the solvent accessibility of a key tryptophan in the C terminus of the BoNT/A-binding domain refines the location of the ganglioside-binding site. Data collected from a single frozen crystal of BoNT/A are included in this study, revealing slight differences in the binding domain orientation as well as density for a previously unobserved translocation domain loop. This loop and the conservation of charged residues with structural proximity to putative pore-forming sequences lend insight into the CNT mechanism of pore formation and translocation. The sequence analysis of the catalytic domain revealed an area near the active-site likely to account for specificity differences between the CNTs. It revealed also a tertiary structure, highly conserved in primary sequence, which seems critical to catalysis but is 30 A from the active-site zinc ion. This observation, along with an analysis of the 54 residue "belt" from the translocation domain are discussed with respect to the mechanism of catalysis.
authors.affiliation: Department of Chemistry, University of California, Berkeley 94720, USA.
authors.forename: D B
authors.initials: DB
authors.lastname: Lacy
authors.forename: R C
authors.initials: RC
authors.lastname: Stevens
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D001692:Biological Transport; D002384:Catalysis; D020134:Catalytic Domain; D003013:Clostridium / Q000737:chemistry / Q000201:enzymology; D017124:Conserved Sequence / Q000235:genetics; D003460:Crystallization; D018360:Crystallography, X-Ray; D005732:Gangliosides / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012997:Solvents; D013329:Structure-Activity Relationship; D013696:Temperature; D013744:Tetanus Toxin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014364:Tryptophan / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D005732:Gangliosides; D012997:Solvents; D013744:Tetanus Toxin; D014364:Tryptophan