Extracytoplasmic protein folding stress signalling as a target for the development of novel antibiotics
Final Report Abstract
There is an urgent medical need for developing novel antibiotics against multiple drug resistant bacterial pathogens that present enormous problems in e.g. hospital acquired infections. Such antibiotics should address novel targets. One promising target is the widely conserved bacterial DegS protein. DegS functions as the rate limiting step in a protein folding stress response signalling cascade that is essential for viability. Therefore, DegS inhibitors are expected to efficiently kill bacterial cells. In work leading to the project, a compound was identified that functions as a selective DegS inhibitor causing lethality in a wide range of bacteria. Modification of this compound lead to a greater than 50 fold improvement in potency. Further characterisations lead to a mechanistic model of inhibition and confirmed that the DegS inhibitor interfered with the activity of the protein folding stress response signalling cascade in living E. coli cells. In addition, a crystal structure of DegS with bound allosteric activator was obtained in which the mechanism of allosteric activation is revealed at unprecedented high resolution. Moreover, a reactive compound class was identified that caused DegS activation by chemical modification. Further characterisations lead to the identification of residues in DegS that are implicated in the mechanism of allosteric activation. Moreover, a panel of 6 mammalian (trypsin, chymotrypsin, elastase, HTRA1, HTRA2 and HTRA3) and 3 E. coli PDZ proteases (DegP, DegQ, Tsp) and the corresponding activity assays was established to assess the selectivity of DegS inhibitors. This platform was employed to determine the selectivity on another class of serine protease inhibitors, Ahpcyclodepsipeptides, that were produced by the Kaiser group in a different context.
Publications
- 2013. The diversity of allosteric regulation in proteases. ACS Chem Biol 8:19-26
Merdanovic, M, Mönig, T, Ehrmann, M and M Kaiser
(See online at https://doi.org/10.1021/cb3005935) - 2017. Tailored Ahp-cyclodepsipeptides as potent non-covalent serine protease inhibitors. Angew. Chem. Int. Ed. Engl. 56:8555-8558
Köcher, S., Rey, J., Bongard, J., Tiaden, A. N., Meltzer, M., Richards, P., Ehrmann, M., and M. Kaiser
(See online at https://doi.org/10.1002/anie.201701771)
