The gene encoding component-II of the Clostridium botulinum C2 toxin was cloned from the chromosomal DNA of C. botulinum type C strain (C)-203U28, and the nucleotide sequence was determined. The gene (bc2h) encodes a protein with 721 amino acid residues and is located at 247 bp downstream of the gene for component-I. The N-terminal 16 amino acids were identical to those obtained by analysis of the purified component-II toxin. The ORF for bc2h had only 39% homology at the amino acid level with the C. perfringens iota-lb protein and an ATP/GTP binding site which is present in the iota-lb protein is missing from the protein encoded by bc2h. Both genes had a homologous region that predicts a transmembrane segment.
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