Subsystem: Putative TldE-TldD proteolytic complex

This subsystem's description is:

Originally the tldE (pmbA) and tldD E.coli mutants were isolated as being resistant to CcdB, a natural poison of gyrase encoded by the CcdA/CcdB poison-antidote system of plasmid F (Murayama, et al., 1996). In addition, the TldE/PmbA protein was implicated in proteolytic maturation of Microcin B17 - a peptide antibiotic produced by Escherichia coli strains carrying the pMccB17 plasmid (Rodriguez-Sainz et al., 1990). The Microcin B17 action mechanism is believed to be similar to that of synthetic quinolones and the bacterial poison CcdB. This led to the idea that TldD and TldE could regulate gyrase function.

However, (Allali et al., 2002) have demonstrated that TldD and TldE proteins form a proteolytically active complex, which acts on antidote CcdA and on pro-MccB17. They have also hypothesized that CcdA and pro-MccB17 were not the only (not the main?) substrates for TldD/TldE protease. This idea was based in part on the phylogenic distribution of the TldD and TldE proteins, which have homologs in genomes of many eubacteria and archaebacteria (including those that do not encode a CcdA/CcdB system or biosynthesis of Microcin B17), suggesting a broader physiological role.

No sequence homology is detectable between pro-MccB17 and CcdA, but their common feature could be a lack of structure. Therefore, (Allali et al., 2002) suggested that TldD and TldE could participate directly or indirectly in biodegradation of unstructured polypeptides. Further experiments will be needed to unravel the physiological role and substrates of these proteins and the way they function.


Allali N, Afif H, Couturier M, Van Melderen L. The highly conserved TldD and TldE proteins of Escherichia coli are involved in microcin B17 processing and in CcdA degradation. From: J Bacteriol. 2002 Jun;184(12):3224-31.

Rodriguez-Sainz, M. C., C. Hernandez-Chico, and F. Moreno. 1990. Molec-
ular characterization of pmbA, an Escherichia coli chromosomal gene re-
quired for the production of the antibiotic peptide MccB17. Mol. Microbiol.

Murayama, N., H. Shimizu, S. Takiguchi, Y. Baba, H. Amino, T. Horiuchi, K. Sekimizu, and T. Miki. 1996. Evidence for involvement of Escherichia coli genes pmbA, csrA and a previously unrecognized gene, tldD, in the control of DNA gyrase by letD (ccdB) of sex factor F. J. Mol. Biol. 256:483502.

For more information, please check out the description and the additional notes tabs, below

Literature ReferencesThe highly conserved TldD and TldE proteins of Escherichia coli are involved in microcin B17 processing and in CcdA degradation. Allali N Journal of bacteriology 2002 Jun12029038
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