F. Cornille et al., COOPERATIVE EXOSITE-DEPENDENT CLEAVAGE OF SYNAPTOBREVIN BY TETANUS TOXIN LIGHT-CHAIN, The Journal of biological chemistry, 272(6), 1997, pp. 3459-3464
The light chain (L chain) of tetanus neurotoxin (TeNT) has been shown
to have been endowed with zinc endopeptidase activity, selectively dir
ected toward the Gln(76)-Phe(77) bond of synaptobrevin, a vesicle-asso
ciated membrane protein (VAMP) critically involved in neuroexocytosis.
In previous reports, truncations at the NH2 and COOH terminus of syna
ptobrevin have shown that the sequence 39-88 of synaptobrevin is the m
inimum substrate of TeNT, suggesting either the requirement of a well
defined three-dimensional structure of synaptobrevin or a role in the
mechanism of substrate hydrolysis for residues distal from the cleavag
e site. In this study, the addition of NH2- and COOH-terminal peptides
of synaptobrevin, S 27-55 (S-1) and S 82-93 (S-2), to the synaptobrev
in fragment S 56-81 allowed the cleavage of this latter peptide by TeN
T to occur. This appears to result from an activation process mediated
by the simultaneous binding of S-1 and S-2 with complementary sites p
resent on TeNT as shown by surface plasmon resonance experiments and t
he determination of kinetic constants. All these results favor an exos
ite-controlled hydrolysis of synaptobrevin by TeNT, probably involving
a conformational change of the toxin. This could account for the high
degree of substrate specificity of TeNT and, probably, botulinum neur
otoxins.