botR/A is a positive regulator of botulinum neurotoxin and associated non-toxin protein genes in Clostridium botulinum A

Mol Microbiol. 1998 Aug;29(4):1009-18. doi: 10.1046/j.1365-2958.1998.00985.x.


The genes of the botulinum neurotoxin A (BoNT) complex are clustered in a locus consisting of two divergent polycistronic operons, one containing the non-toxic, non-haemagglutinin (NTNH) component and bontA genes, the other containing the haemagglutinin (HA) component genes. The two operons are separated by a gene (botR/A, previously called orf21) encoding a 21 kDa protein. A recombinant Clostridium botulinum A strain that overexpresses botR/A was constructed by electroporating strain 62 with the vector pAT19 containing botR/A under the control of its own promoter. The transformed strain produced more BoNT/A and associated non-toxic proteins (ANTPs) and the corresponding mRNAs than the non-transformed strain. Partial inhibition of botR/A by antisense mRNA resulted in lower levels of BoNT/A, NTNH and HA70 and the levels of the corresponding mRNAs. Gel mobility shift assays and immunoprecipitations showed that BotR/A bound to the DNA promoter region upstream from the two BoNT/A complex operons. These results show that botR/A activated transcription of the genes encoding BoNT/A and ANTPs in C. botulinum A by interacting directly with the region promoter, and that the homologous genes in C. botulinum B, C and D presumably have the same function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Proteins / biosynthesis
  • Bacterial Proteins / genetics
  • Base Sequence
  • Binding Sites / genetics
  • Botulinum Toxins / biosynthesis
  • Botulinum Toxins / genetics*
  • Botulinum Toxins / toxicity
  • Clostridium botulinum / genetics*
  • Clostridium botulinum / metabolism
  • DNA Primers / genetics
  • Gene Expression
  • Genes, Bacterial*
  • Genes, Regulator
  • Mice
  • Multigene Family
  • Operon
  • Promoter Regions, Genetic
  • RNA, Antisense / genetics
  • RNA, Bacterial / genetics
  • RNA, Bacterial / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Recombination, Genetic


  • Bacterial Proteins
  • DNA Primers
  • RNA, Antisense
  • RNA, Bacterial
  • RNA, Messenger
  • Botulinum Toxins