The Mechanism of Inhibition of Botulinum Neurotoxin Type A by Two Quinolinol Compounds
Abstract
The potential of Botulinum neurotoxins (BoNTs) to be used as biological weapons makes the need to identify small molecule inhibitors critical but it is a challenging target due to the large substrate‐enzyme interface. BoNTs are produced by the bacterium Clostridium botulinum in seven antigenically distinct serotypes (A‐G), with serotype A (BoNT/A) being the most potent toxin known to man. Recently, quinolinol‐based compounds have been identified as a promising starting point for effective BoNT/A inhibitors. Understanding the mechanism of inhibition by quinolinol compounds would facilitate inhibitor optimization studies. In this study, a Foster resonance energy transfer (FRET) based substrate of BoNT/A, SNAPtide, was used to study the mechanism of inhibition of BoNT/A endopeptidase activity by two new quinolinol compounds, MSU58 and MSU84, with IC50 values of 3.3 μM and 5.8 μM, respectively. Kinetic analysis and model discrimination analysis revealed both compounds to be competitive inhibitors of BoNT/A endopeptidase activity. Inhibition constants (KI) were found to be 3.2 μM for MSU58 and 6.2 μM for MSU84. The kinetic rate constant for the binding and release of substrate and inhibitor were also determined. These data indicate that these inhibitors bind in the active site of BoNT/A and that binding is mutually exclusive with the binding of the substrate. This study, is the first to report on the competitive inhibition of BoNT/A by a quinolinol group of compounds. These data help define the inhibitor binding pocket and, along with structure activity relationship studies, provide immediate direction for further compound synthesis.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Apr 01, 2017
- Source ID
- 10.1096/fasebj.31.1_supplement.921.1
Entities
People
- David P. Rotella
- Nina M Goodey
- Ronald Goldberg
- Sreedhar R. Tummalapalli
- Yacoba Vroom Teschemaker Minnow
Organizations
- Montclair State University
- United States Army Medical Research and Development Command