DEVELOPING PEPTIDIC INIHIBATORS FOR E.COLI MAZF TOXIN PROTEIN

One of the challenges in antibiotic treatment is the re-infection that may be caused by persister cells. These sub-population bacterial cells enter a state of dormancy and therefore are not affected by antibiotic treatment. The development of persister cells seems to be induced by bacterial Toxin-Antitoxin (TA) systems. Reducing or preventing the presence of persister cells may abrogate re-infection after antibiotic treatment (1).

TA systems are composed from toxin and antitoxin proteins. In the Escherichia coli mazEF TA system, the toxin mazF is an endoribonuclease and the antitoxin mazE binds mazF in a complex that prevents mazF catalytic activity. The antitoxin is less stable, and when it is being degraded the toxin is released and may induce bacterial cell death (2).

Our goal is to study the Escherichia coli mazEF TA system at the molecular level using peptides based tools. In the current research we designed and synthesized peptides based on structural and biochemical findings. Both toxin and antitoxin proteins were expressed and purified in high yield and purity. mazF endoribonuclease catalytic activity was measured using a fluorometric assay (FRET) (3). We characterized the effect of the designed peptides on mazF catalytic activity. We have found a peptide that inhibits mazF activity at low micromolar concentrations. We are currently studying the effect of our peptides on E.coli cells in vivo to better understand its biological role. In the future our new compounds may be used as a combined treatment with antibiotics to prevent re-infection.

1.Maisonneuvea , L. J. Shakespearea , M. G. Jørgensenb , & K. Gerdesa. Bacterial persistence by RNA endonucleases. PNAS, 2011. 108: 13206–13211.

2.Belitsky, H. Avshalom, A. Erental, I. Yelin, S. Kumar, N. London, M. Sperber, O. Schueler-Furman, & H. Engelberg-Kulka. The Escherichia coli Extracellular Death Factor EDF Induces the Endoribonucleolytic Activities of the Toxins MazF and ChpBK. Molecular Cell, 2011. 41: 625–635.

3.Wang, P. J. Hergenrother. A continuous fluorometric assay for the assessment of MazF ribonuclease activity. Analytical Biochemistry, 2007. 371: 173–183.