FtsH proteins have dual chaperone-protease activities and are involved in protein
quality control under stress conditions. Although the functional role of FtsH proteins has been clearly established, the regulatory mechanisms controlling ftsH expression in
gram-positive bacteria remain largely unknown. Here we show that ftsH of
Lactobacillus plantarum WCFS1 is transiently induced at the
transcriptional level upon a temperature upshift. In addition, disruption of ftsH negatively affected the growth of
L. plantarum at high temperatures.
Sequence analysis and mapping of the ftsH
transcriptional start site revealed a potential
operator sequence for the CtsR
repressor, partially overlapping the -35 sequence of the ftsH
promoter. In order to verify whether CtsR is able to recognize and bind the ftsH
promoter, CtsR proteins of
Bacillus subtilis and
L. plantarum were overproduced, purified, and used in
DNA binding
assays. CtsR from both species bound specifically to the ftsH
promoter, generating a single
protein-DNA complex, suggesting that CtsR may control the expression of
L. plantarum ftsH. In order to confirm this hypothesis, a DeltactsR
mutant strain of
L. plantarum was generated. Expression of ftsH in the DeltactsR
mutant strain was strongly
upregulated, indicating that ftsH of
L. plantarum is negatively controlled by CtsR. This is the first example of an ftsH gene controlled by the CtsR
repressor, and the first of the low-G+C
gram-positive bacteria where the regulatory mechanism has been identified.
