Rational design of botulinum neurotoxin A1 mutants with improved oxidative stability. (1st June 2018) - López de la Paz, Manuela
Abstract: Botulinum neurotoxins (BoNTs) are the most potent toxic proteins to mankind known but applied in low doses trigger a localized muscle paralysis that is beneficial for the therapy of several neurological disorders and aesthetic treatment. The paralytic effect is generated by the enzymatic activity of the light chain (LC) that cleaves specifically one of the SNARE proteins responsible for neurotransmitter exocytosis. The activity of the LC in a BoNT-containing therapeutic can be compromised by denaturing agents present during manufacturing and/or in the cell. Stabilization of the LC by reducing vulnerability towards denaturants would thus be advantageous for the development of BoNT-based therapeutics. In this work, we focused on increasing the stability of LC of BoNT/A1 (LC/A1) towards oxidative stress. We tackled this task by rational design of mutations at cysteine and methionine LC/A1 sites. Designed mutants showed improved oxidative stability in vitro and equipotency to wildtype toxin in vivo . Our results suggest that suitable modification of the catalytic domain can lead to more stable BoNTs without impairing their therapeutic efficacy. Highlights: Stabilization of the light chain of botulinum neurotoxin A1 (LC/A1) towards oxidation was approached by rational design. All methionine and cysteine residues of LC/A1 were considered for the in silico design of mutants. Designed mutants were selected based on predicted hydropathy and stability changes respect to wildtype (WT) LC/A1. The mutant M106L, M253L, M411Q was more resistant against oxidation in vitro than WT toxin without loss of potency in vivo .