Faculty Collaboration Database

Botulinum Neurotoxin A4 Has a 1000-Fold Reduced Potency Due to Three Single Amino Acid Alterations in the Protein Receptor Binding Domain. Int J Mol Sci 2023 Mar 16;24(6)

Date

03/30/2023

Pubmed ID

36982762

Pubmed Central ID

PMC10055998

DOI

10.3390/ijms24065690

Scopus ID

2-s2.0-85151111423 (requires institutional sign-in at Scopus site)   1 Citation

Abstract

Botulinum neurotoxin subtype A4 (BoNT/A4) is ~1000-fold less potent than BoNT/A1. This study addresses the basis for low BoNT/A4 potency. Utilizing BoNT/A1-A4 and BoNT/A4-A1 Light Chain-Heavy Chain (LC-HC) chimeras, HC-A4 was responsible for low BoNT/A4 potency. Earlier studies showed BoNT/A1-receptor binding domain (Hcc) bound a β-strand peptide (556-564) and glycan-N⁵⁵⁹ within Luminal Domain 4 (LD4) of SV2C, the BoNT/A protein receptor. Relative to BoNT/A1, the Hcc of BoNT/A4 possesses two amino acid variants (D¹¹⁴¹ and N¹¹⁴²) within the β-peptide binding interface and one amino acid variant (R¹²⁹²) located near the SV2C glycan-N⁵⁵⁹. Introduction of BoNT/A4 β-strand peptide variant (D¹¹⁴¹ and N¹¹⁴²) into BoNT/A1 reduced toxin potency 30-fold, and additional introduction of the BoNT/A4 glycan-N⁵⁵⁹ variant (D¹¹⁴¹, N¹¹⁴², and R¹²⁹²) further reduced toxin potency to approach BoNT/A4. While introduction of BoNT/A1 glycan-N⁵⁵⁹ variant (G¹²⁹²) into BoNT/A4 did not alter toxin potency, additional introduction of BoNT/A1 β-strand peptide variants (G¹¹⁴¹, S¹¹⁴², and G¹²⁹²) resulted in potency approaching BoNT/A1 potency. Thus, outcomes from these functional and modeling studies indicate that in rodent models, disruption of Hcc -SV2C β-peptide and -glycan-N⁵⁵⁹ interactions mediate low BoNT/A4 potency, while in human motor neurons, disruption of Hcc-SV2C β-peptide alone mediates low BoNT/A4 potency, which link to a species-specific variation at SV2C⁵⁶³.

Author List

Tepp WH, Bradshaw M, Gardner AP, Kaufman RL, Barbieri JT, Pellett S

Author

Joseph T. Barbieri PhD Professor in the Microbiology and Immunology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Amino Acids
Humans
Protein Binding
Protein Domains