“Role of the two ClpP protease subunits in Mycobacterium tuberculosis”
Abstract
Caseinolytic (Clp) proteases are the most widespread energy-dependent
proteases in bacteria. They are involved in protein quality control by degrading
misfolded and aggregated proteins and have a role in regulatory proteolysis.
The main group of substrates of the Clp proteases is the SsrA-tagged proteins,
which arise in the presence of defective translation. SsrA tagging is carried out
by tmRNA, encoded by ssrA, together with a protein partner SmpB. While most
organisms have only one ClpP, Mycobacterium tuberculosis has two ClpP
protease subunits (ClpP1 and ClpP2) with at least one of them essential for
growth. Co-expression of clpP1 and clpP2 was demonstrated showing that
clpP1 and clpP2 are not expressed under different conditions. The promoter
region of clpP1P2 was identified, together with the potential ClgR binding site.
A reporter system to assay ClpP1 and ClpP2 enzymatic activities was
developed based on LacZ incorporating SsrA tag sequences. This showed that
both ClpP1 and ClpP2 degrade SsrA-tagged LacZ, whilst only ClpP2 degrades
untagged proteins. This suggests different pattern recognition for the two ClpP
proteins with substrate recognition by ClpP1 dependent on the last three
residues of the C-terminus of the tag sequence. Mutagenesis analysis of the
accessory components demonstrated that ssrA is essential but SmpB deletion
is viable. SmpB is not required for aerobic growth but the smpBΔ mutant strain
was more sensitive to antibiotics targeting the ribosome as compared to wildtype
cells.
Authors
Personne, YoannCollections
- Theses [3705]