6ui1

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Crystal structure of BoNT/A-LCHn domain in complex with VHH ciA-D12, ciA-B5, and ciA-H7

Structural highlights

6ui1 is a 4 chain structure with sequence from Clostridium botulinum and Vicugna pacos. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	X-ray diffraction, Resolution 2.2000086Å
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

BXA1_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 PubMed

Botulinum neurotoxin (BoNT) is one of the most acutely lethal toxins known to humans, and effective treatment for BoNT intoxication is urgently needed. Single-domain antibodies (VHH) have been examined as a countermeasure for BoNT because of their high stability and ease of production. Here, we investigate the structures and the neutralization mechanisms for six unique VHHs targeting BoNT/A1 or BoNT/B1. These studies reveal diverse neutralizing mechanisms by which VHHs prevent host receptor binding or block transmembrane delivery of the BoNT protease domain. Guided by this knowledge, we design heterodimeric VHHs by connecting two neutralizing VHHs via a flexible spacer so they can bind simultaneously to the toxin. These bifunctional VHHs display much greater potency in a mouse co-intoxication model than similar heterodimers unable to bind simultaneously. Taken together, our studies offer insight into antibody neutralization of BoNTs and advance our ability to design multivalent anti-pathogen VHHs with improved therapeutic properties.

Structural Insights into Rational Design of Single-Domain Antibody-Based Antitoxins against Botulinum Neurotoxins.,Lam KH, Tremblay JM, Vazquez-Cintron E, Perry K, Ondeck C, Webb RP, McNutt PM, Shoemaker CB, Jin R Cell Rep. 2020 Feb 25;30(8):2526-2539.e6. doi: 10.1016/j.celrep.2020.01.107. PMID:32101733^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ Lam KH, Tremblay JM, Vazquez-Cintron E, Perry K, Ondeck C, Webb RP, McNutt PM, Shoemaker CB, Jin R. Structural Insights into Rational Design of Single-Domain Antibody-Based Antitoxins against Botulinum Neurotoxins. Cell Rep. 2020 Feb 25;30(8):2526-2539.e6. PMID:32101733 doi:10.1016/j.celrep.2020.01.107