Botulinum Neurotoxin Type C Cleaves a Single Lys-Ala Bond within the Carboxyl-terminal Region of Syntaxins

Abstract

Botulinum neurotoxin serotype C (BoNT/C) is a 150-kDa protein produced by Clostridium botulinum, which causes animal botulism. In contrast to the other botulinum neurotoxins that contain one atom of zinc, highly purified preparations of BoNT/C bind two atoms of zinc per toxin molecule. BoNT/C is a zinc-endopeptidase that cleaves syntaxin 1A at the Lys253-Ala254 and syntaxin 1B at the Lys252-Ala253 peptide bonds, only when they are inserted into a lipid bilayer. The other Lys-Ala bond present within the carboxyl-terminal region is not hydrolyzed. Syntaxin isoforms 2 and 3 are also cleaved by BoNT/C, while syntaxin 4 is resistant. These data suggest that BoNT/C recognizes a specific spatial organization of syntaxin, adopted upon membrane insertion, which brings a selected Lys-Ala peptide bond of its carboxyl-terminal region to the active site of this novel metalloproteinase.

Botulinum neurotoxin light chains inhibit both Ca2+‐induced and GTP analogue‐induced catecholamine release from permeabilised adrenal chromaffin cells

“…The requirement for the other two neurotoxin sensitive substrates for secretion due to Ca 2+ or GppNHp in chromaffin cells was examined using recombinant light chains of the botulinum C1 neurotoxin, which was shown to preferentially cleave syntaxin [42,43] and E neurotoxin which cleaves SNAP-25 [44,45]. The maximum concentration of these light chains that could be used was limited by their instability following dialysis.…”

OSM1/SYP61: A Syntaxin Protein in Arabidopsis Controls Abscisic Acid–Mediated and Non-Abscisic Acid–Mediated Responses to Abiotic Stress

“…However, the three sites necessary for binding and cleavage by Bot N/C (Schiavo et al, 1995;O'Connor et al, 1997), which are present on Nt-Syr1 (Leyman et al, 1999) and associated with sensitivity to the toxin, are poorly conserved in OSM1/SYP61 ( Figure 12B). Although it remains unproven that OSM1/SYP61 is not sensitive to Bot N/C, this finding suggests that there may be another Arabidopsis SNARE protein that has a similar function, because Leyman et al (1999) were able to inhibit ABA-induced Cl Ϫ channel current in tobacco guard cells with Bot N/C treatment.…”

“…It is interesting as well that syntaxin appears to be required for tethering to membrane sites of the Ca 2ϩ channel that affects neurotransmitter release, ensuring G-protein OSM1/SYP61, Arabidopsis; STX6_MOUSE, syntaxin 6 from mouse; STX6_HUMAN, syntaxin 6 from human; STX10_HUMAN, syntaxin 10 from human. Sequences shown above the aligned sequences are two predicted Clostridium botulinum toxin C1 recognition sites (FMEEFFEQVE and ELEDMLESGN, respectively) and a cleavage site (AVKYQSKAR) from squid syntaxin (Schiavo et al, 1995;O'Connor et al, 1997). (C) Sequence alignment in the t-SNARE coiled-coil domain.…”

Syntaxin 1A Modulates the Voltage-gated L-type Calcium Channel (Cav1.2) in a Cooperative Manner

“…Although essential, the Cys residues are not sufficient for conferring inhibition of current amplitude because a chimeric syntaxin 2 containing Sx1A TMD does not inhibit ion currents (12). Moreover, cleavage of Sx1A by botulinum toxin C1 close to the TMD at amino acid 253/254 (40) partially uncouples the syntaxin-channel interface, in turn abolishing inhibition of current amplitude (12). In contrast, in both experiments the Sx1A effect on channel activation was apparent, indicating that the cytosolic region of Sx1A contains channel interacting domains that contribute both to kinetic modulation and channel inhibition.…”