C-terminal processing protease inhibitors as antibacterial drugs

C-terminal processing proteases (CTPs) which can be found in a broad range of different organisms ranging from prokaryotes such as Eubacteria, Archaea to eukaryotes such as algae, plants and animals. CTPs are classified in the MEROPS peptidase database as family S41 (merops.sanger.ac.uk). As their name hints, CTPs cleave a small portion of the carboxy-terminus of specific substrate proteins. In plants, algae and cyanobacteria CTPs have a very specific function in activating the pre-D1 protein which is essential for photosynthesis by cleaving of a small C-terminal peptide. In bacteria knowledge about CTP function is still very limited but CTPs seem to influence multiple basal physiological functions and virulence of pathogens.  We have shown in the opportunistic pathogen Pseudomonas aeruginosa that CTPs may cleave Penicillin-Binding-Proteins. Penicillin-Binding-Proteins play a role in the cell wall synthesis of bacteria. Besides that we were able to show that inactivation of the CTPs in this organism results in a drastic loss of virulence as proven in different animal infection models. This reduction of virulence can probably be explained by the fact that inactivation of the CTPs leads to a reduced secretion of virulence factors and toxins which play a major role in infection.  On the way to potential novel antibiotics we are currently developing peptide based inhibitors for bacterial CTP proteases. This new approach aims on “disarming” pathogens rather than fast killing as conventional antibiotics do. The idea behind this strategy is the reduction of selective pressure by these next generation anti bacterial drugs.


1.      Prof. L. Rahme, Harvard Medical School/ Boston Hospital, USA

2.      Dr. S. Nabuurs, Center for Molecular and Biomolecular Informatics, Nijmegen, The Netherlands

3.      Dr. D. Girones, Lead Pharma Holding B.V., the Netherlands.

4.      Prof. K.-E. Jaeger, Institute of Molecular Enzyme Technology, Helmholtz Research Center Jülich, Germany

5.      Prof. J. Pietruszka, Institute of Bioorganic Chemistry, Helmholtz Research Center Jülich, Germany

Initial work of R. H. at the IMET Juelich has been funded by the EU FP6 Research Strategy to Antimicrobial Drug Resistance

Figure 1: 3D structure of a CTP of S. obliquus. Part A represents the PDZ domain which is probably necessary of substrate recognition. Part B represents the active domain in which cleavage occurs.  The yellow string represents a peptide backbone in a possible substrate recognition configuration. This study was done in cooperation which Dr. D. Girones and Dr. S. Nabuurs of Lead Pharma Holding B.V., the Netherlands.



Figure 2: Docking studies of potential protease inhibitors for CTPs of P.aeruginosa. This study was done in cooperation which dr. D. Girones and dr. S. Nabuurs of Lead Pharma Holding B.V., the Netherlands.