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Catalytic Site Atlas

CSA LITERATURE entry for 1i1e

E.C. namebontoxilysin
SpeciesClostridium botulinum (strain ATCC 19397 / Type A)
E.C. Number (IntEnz) 3.4.24.69
CSA Homologues of 1i1eThere are 64 Homologs
CSA Entries With UniProtID P10844
CSA Entries With EC Number 3.4.24.69
PDBe Entry 1i1e
PDBSum Entry 1i1e
MACiE Entry 1i1e

Literature Report

IntroductionBotulinum neurotoxin acts by inhibiting neurotransmitter release. It binds to peripheral neuronal synapses, is internalised and moves by retrograde transport up the axon into the spinal cord where it can move between postsynaptic and presynaptic neurons. It disrupts neurotransmitter release by acting as a zinc endopeptidase that cleaves the 76-Gln-|-Phe-77 bond of synaptobrevin-2(Sb2), one of three SNARE proteins involved in neuronal synaptic vesicle fusion.
There are in total 7 serotypes of botulinum neurotoxin. All seven serotypes possess an identical Zn2+-binding motif, HEXXH, but are unique either in substrate selection or in their cleavage site. Their catalytic domains share high degree of sequence homology and holotoxin structures of serotype A and serotype B have been reported to be structurally similar.
Botulinum belongs to the same class of neurotoxin with tetanus neurotoxin and they share significant sequence homology. They possess similar structural and functional domains and have a similar mechanism of toxicity. However, Botulinum neurotoxins acts at the neuromuscular junction causing flaccid paralysis, while tetanus toxin acts at the central nervous system causing spastic paralysis.
MechansimGlu267 is a base to deprotonate the water molecule. It acts in conjunction with Zn2+ to activate the water molecule. The activated water molecule acts as a nucleophile to attack the carbonyl of the peptide bond. Arg369 and Zn2+ stabilise the transition state by interacting with the negative charged carbonyl oxygen atom of Sb2 Gln 76 of the tetrahedral intermediate. Tyr372 stabilises the transition state by donating a proton to the amide nitrogen of Sb2 Phe77 in the transition state, allowing the conversion of the amine to a more favourable, protonated leaving group. The peptide bond finally cleaves as product formation is favourable.
Reaction

Catalytic Sites for 1i1e

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
TyrA372373macie:sideChainIt donates a proton to the amide nitrogen of Sb2 Phe77 in the transition state, allowing the conversion of the amine to a more favourable, protonated leaving group, assisting the hydrolysis reaction to yield the cleaved product.
ArgA369370macie:sideChainIt stabilises the transition state by stabilising the negative charge developed on the substrate carbonyl oxygen atom of Sb2 Gln 76.
GluA267268macie:sideChainIt activates water to allow its nucleophilic attack on the peptide bond by deprotonating it and it acts in conjunction with Zn2+ ion.

Literature References

Notes:
Swaminathan S
Structural analysis of the catalytic and binding sites of Clostridium botulinum neurotoxin B.
Nat Struct Biol 2000 7 693-699
PubMed: 10932256
Hanson MA
Cocrystal structure of synaptobrevin-II bound to botulinum neurotoxin type B at 2.0 A resolution.
Nat Struct Biol 2000 7 687-692
PubMed: 10932255
Schiavo G
Botulinum neurotoxins are zinc proteins.
J Biol Chem 1992 267 23479-23483
PubMed: 1429690
Rigoni M
Site-directed mutagenesis identifies active-site residues of the light chain of botulinum neurotoxin type A.
Biochem Biophys Res Commun 2001 288 1231-1237
PubMed: 11700044
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