Nucleotide Sequence of the Gene Coding for Proteolytic (Group I) Clostridium botulinum Type F Neurotoxin: Genealogical Comparison with other Clostridial Neurotoxins

Botulinum neurotoxin type F can be produced by proteolytic or non-proreolytic strains of C. botulinum, or from C. baratii. In recent years, the sequences of all toxin types except that of proteolytic type F toxin have been determined. We have cloned the neurotoxin gene from proteolytic C. botulinum (type F Langeland) as a series of overlapping PCR fragments, and determined the nucleotide sequence. The translated sequence demonstrates a toxin of 1278 amino acid residues, which has highest similarity with non-proteolytic type F toxin. Phylogenetic trees based on toxin sequences show that the type F sequences fall into a naturally distinct group, although the strains producing these toxins are not phylogenetically closely related.