Proteolysis of SNAP-25 isoforms by botulinum neurotoxin types A, C, and E: domains and amino acid residues controlling the formation of enzyme-substrate complexes and cleavage.

摘要: Tetanus toxin and the seven serologically distinct botulinal neurotoxins (BoNT/A to BoNT/G) abrogate synaptic transmission at nerve endings through action of their light chains (L chains), which proteolytically cleave VAMP (vesicle-associated membrane protein)/synaptobrevin, SNAP-25 (synaptosome-associated protein 25 kDa), or syntaxin. BoNT/C was reported proteolyze both syntaxin SNAP-25. Here, we demonstrate that cleavage occurs between Arg198 Ala199, depends on presence regions Asn93 Glu145 Ile156 Met202, requires about 1,000-fold higher L chain concentrations in comparison with BoNT/A BoNT/E. Analyses BoNT/E sites revealed changes carboxyl-terminal residues, contrast amino-terminal drastically impair proteolysis. A inactive mutant failed bind VAMP/synaptobrevin syntaxin, but formed a stable complex (KD = 1.9 x 10(-7) M) The minimal essential domain required for by involves segment Met146-Gln197, binding optimal only full-length Proteolysis Ile156-Asp186. Murine SNAP-23 cleaved and, reduced extent, BoNT/A, whereas human resistant all clostridial chains. Lys185Asp Pro182Arg mutations induced susceptibility toward BoNT/E, respectively.