Synaptotagmin Binding to Botulinum Neurotoxins

Area of Science:

• Neuroscience
• Biochemistry
• Molecular Biology

Background:

• Botulinum neurotoxins (BoNTs) are potent toxins used therapeutically.
• BoNTs bind to ganglioside and protein receptors on neuronal cells.
• Species-specific differences in protein receptors affect BoNT binding and toxicity.

Purpose of the Study:

• Investigate the binding of BoNT/B, /DC, and /G to synaptotagmin I and II (Syt-I, Syt-II) from different species.
• Determine the impact of species origin on BoNT-Syt binding affinity.
• Identify the specific regions of Syt involved in BoNT binding.

Main Methods:

• Isothermal titration calorimetry (ITC) to measure binding affinities.
• Saturation transfer difference (STD) NMR to identify binding epitopes.
• STD-Total Correlation Spectroscopy (STD-TOCSY) NMR for detailed structural analysis.

Main Results:

• BoNT/G showed highest affinity for human Syt-I; BoNT/DC showed highest affinity for bovine Syt-II.
• BoNT/B, /DC, and /G exhibited low binding to human Syt-II.
• NMR revealed Syt peptide regions interacting with BoNT/G, similar to the BoNT/B-Syt-II complex.
• Regions outside the direct binding site influence peptide helicity and affinity.

Conclusions:

• Species of origin significantly impacts BoNT-Syt binding affinity.
• Structural insights into BoNT-Syt interactions can be gained using NMR.
• Understanding these interactions is crucial for optimizing BoNT-based therapies.