Epitope mapping of botulinum neurotoxins light chains

► Random fragments of BoNT/A light chain were screened with rabbit anti-BoNT/A serum. ► Four separate epitope-forming regions were determined. ► Epitopes in other serotypes were determined by alignment of sequences. ► Epitopes retain their structure even when incorporated into other proteins. ► α-toxin of Clostridium perfringens can carry foreign polypeptides outside of the Escherichia coli cell.