TetR is a positive regulator of the tetanus toxin gene in Clostridium tetani and is homologous to botR.
The TetR gene immediately upstream from the tetanus toxin (TeTx) gene was characterized. It encodes a 21,562-Da protein which is related (50 to 65% identity) to the equivalent genes (botR) in Clostridium botulinum. TetR has the feature of a DNA binding protein with a basic pI (9.53). It contains a helix-turn-helix motif and shows 29% identity with other putative regulatory genes in Clostridium, i.e., uviA from C. perfringens and txeR from C. difficile. We report for the first time the transformation of C. tetani by electroporation, which permitted us to investigate the function of tetR. Overexpression of tetR in C. tetani induced an increase in TeTx production and in the level of the corresponding mRNA. This indicates that TetR is a transcriptional activator of the TeTx gene. Overexpression of botR/A (60% identity with TetR at the amino acid level) in C. tetani induced an increase in TeTx production comparable to that for overexpression of tetR. However, botR/C (50% identity with TetR at the amino acid level) was less efficient. This supports that TetR positively regulates the TeTx gene in C. tetani and that a conserved mechanism of regulation of the neurotoxin genes is involved in C. tetani and C. botulinum.
Marvaud
J C
JC
Unité des Toxines Microbiennes, Institut Pasteur, 75724 Paris Cedex 15, France.
Eisel
U
U
Binz
T
T
Niemann
H
H
Popoff
M R
MR
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins; D001483:Base Sequence; D001905:Botulinum Toxins / Q000096:biosynthesis; D003014:Clostridium botulinum; D003017:Clostridium tetani / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005809:Genes, Regulator; D007928:Lethal Dose 50; D051379:Mice; D008969:Molecular Sequence Data; D012097:Repressor Proteins / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D013744:Tetanus Toxin / Q000096:biosynthesis / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics*
D001426:Bacterial Proteins; C116103:BotR protein, Clostridium botulinum; D012097:Repressor Proteins; C116102:TetR protein, Clostridium tetani; D013744:Tetanus Toxin; D015534:Trans-Activators; C034811:tetracycline resistance-encoding transposon repressor protein; D001905:Botulinum Toxins