4iqp | pdb_00004iqp
Crystal Structure of HCRA-W1266A
Structural highlights
FunctionBXA1_CLOBH Inhibits acetylcholine release. The botulinum toxin binds with high affinity to peripheral neuronal presynaptic membrane to the secretory vesicle protein SV2. It binds directly to the largest luminal loop of SV2A, SV2B and SV2C. It is then internalized by receptor-mediated endocytosis. The C-terminus of the heavy chain (H) is responsible for the adherence of the toxin to the cell surface while the N-terminus mediates transport of the light chain from the endocytic vesicle to the cytosol. After translocation, the light chain (L) hydrolyzes the 197-Gln-|-Arg-198 bond in SNAP-25, thereby blocking neurotransmitter release. Inhibition of acetylcholine release results in flaccid paralysis, with frequent heart or respiratory failure. Publication Abstract from PubMedThe need for a vaccine against botulism has increased since the discontinuation of the Pentavalent (ABCDE) Botulinum Toxoid Vaccine by the Centers for Disease Control and Prevention. The Botulinum toxins (BoNTs) are the primary virulence factors and vaccine components against botulism. BoNTs comprise three domains which are involved in catalysis (LC), translocation (HCT) and host receptor binding (HCR). Recombinant HCR subunits have been used to develop the next generation of BoNT vaccine. Using structural studies and the known entry properties of the BoNT/A, an HCR subunit vaccine against BoNT/A was designed that contained the point mutation W1266A within the ganglioside binding pocket. HCR/A(W1266A) did not enter primary neurons and the crystal structure of HCR/A(W1266A) was virtually identical to wild type HCR/A. Using a mouse model, experiments were performed using a high dose vaccine and a low dose vaccine. At high vaccine dose, HCR/A and HCR/A(W1266A) elicited a protective immune response to BoNT/A challenge. At the low dose vaccination, HCR/A(W1266A) was a more protective vaccine than HCR/A. alpha-HCR IgG titers correlated with protection from BoNT challenge, although titers to block HCR/A entry were greater in serum in HCR/A vaccinated mice relative to HCR/A(W1266A) vaccinated mice. This study shows that removal of receptor binding capacity enhances potency of the subunit HCR vaccine. Vaccines that lack receptor binding capacity have the added property of limited off-target toxicity. Enhancing the Protective Immune Response against Botulism.,Przedpelski A, Tepp WH, Kroken AR, Fu Z, Kim JJ, Johnson EA, Barbieri JT Infect Immun. 2013 May 13. PMID:23670557[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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