title: The C-terminus of Botulinum A Protease Has Profound and Unanticipated Kinetic Consequences Upon the Catalytic Cleft.
abstract: Botulinum 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 possess 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, alpha-exosite and beta-exosite inhibitors versus truncated and full length enzyme. Molecular dynamics simulations conducted with the truncated and homology models of the fully 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 (alpha-exosite) inhibitors remain equipotent.
authors.affiliation: Departments of Chemistry and Immunology, and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Rd., La Jolla, CA, 92037, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Silhár
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Lardy
authors.forename: Mark S
authors.initials: MS
authors.lastname: Hixon
authors.forename: Charles B
authors.initials: CB
authors.lastname: Shoemaker
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Barbieri
authors.forename: Anjali K
authors.initials: AK
authors.lastname: Struss
authors.forename: Jenny M
authors.initials: JM
authors.lastname: Lively
authors.forename: Sacha
authors.initials: S
authors.lastname: Javor
authors.forename: Kim D
authors.initials: KD
authors.lastname: Janda
keywords: Botulinum neurotoxin; natural product; protease inhibitor; small molecule inhibitor; zinc-dependent metalloprotease
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