ml300428s_si_001.pdf (422.51 kB)
C‑Terminus of Botulinum A Protease Has Profound and Unanticipated Kinetic Consequences upon the Catalytic Cleft
journal contribution
posted on 2013-02-14, 00:00 authored by Peter Šilhár, Matthew A. Lardy, Mark S. Hixon, Charles B. Shoemaker, Joseph T. Barbieri, Anjali K. Struss, Jenny M. Lively, Sacha Javor, Kim D. JandaBotulinum neurotoxins (BoNTs) are among the most deadly
poisons
known, though ironically, they also are of great therapeutic utility.
A number of research programs have been initiated to discover small
molecule inhibitors of BoNTs metalloprotease activity. Many, though
not all, of these programs have screened against a truncated and more
stable form of the enzyme, that possesses comparable catalytic properties
to the full length enzyme. Interestingly, several classes of inhibitors,
notably the hydroxamates, display a large shift in potency between
the two enzyme forms. In this report we compare the kinetics of active-site,
α-exosite and β-exosite inhibitors versus truncated and
full length enzyme. Molecular dynamics simulations conducted with
the truncated and homology models of the full length BoNT LC/A indicate
the flexibility of the C-terminus of the full length enzyme is responsible
for the potency shifts of active-site proximally binding inhibitors
while distal binding (α-exosite) inhibitors remain equipotent.