Prevention of aggregation and autocatalysis for sustaining biological activity of recombinant BoNT/A-LC upon long-term storage.

Protein aggregation during expression, purification, storage, or transfer into requisite assay buffers hampers the use of proteins for in vitro studies. The formation of these aggregates represents a major obstacle in the study of biological activity and also restricts the spectrum of protein products being available for the biomedical applications. The catalytic light chain of botulinum neurotoxin type A undergoes autocatalysis and aggregation after purification upon long-term storage and freeze-thawing. In present study the conditions for the high level expression and purification of biologically active light chain protein of botulinum neurotoxin were optimized from a synthetic gene. Several co-solvents were screened in order to prevent autocatalysis and aggregation of rBoNT/A-LC. The effect of the co-solvents is studied on endopeptidase activity during long term storage of the recombinant protein. The purified rBoNT/A-LC was also evaluated for its immunogenicity.