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Postdoctoral position, Biochemistry (May 2008)

 

A postdoctoral position in biochemistry is available at LRMA (INSERM-University Paris 5 and 6). Our laboratory studies the evolution of the peptidoglycan assembly pathway in response to the selective pressure of antibiotics (1). Our work focuses on novel by-pass mechanisms of resistance, the identification of novel drug targets, and the design of inhibitors. The position available immediately concerns the Fem family of non-ribosomal peptidyl transferases that use aminoacyl-tRNAs as the amino acid donor to synthesize the peptidoglycan cross-bridge in many species of pathogenic Gram-positive bacteria.  We have recently achieved the in vitro synthesis of the entire side chain of the peptidoglycan precursors of Enterococcus faecalis using purified transferases, aminoacyl-tRNA synthases, tRNA, and peptidoglycan precursors (2,3). We have also determined the 3D structure of the FemX transferase and of a complex formed with its first substrate (UDP-MurNAc-pentapetide) (4,5,6) and investigated the role of Fem transferases in peptidoglycan cross-linking by the penicillin binding proteins (7) and by L,D-transpeptidases (8). Recently, we have started to analyze the interaction of Fem transferases with the second substrate, the tRNA (9) and with a first class of inhibitors that act as stable tRNA analogues (10). Further development of the project by the candidate will include (i) the elucidation of the catalytic mechanism of the enzymes (ii) the analysis of their substrate specificity using mis-acylated tRNA obtained by chemical acylation, (iii) the identification of the respective role of natural tRNAs in peptidoglycan and protein synthesis, and (iv) the determination of the structure of a ternary complex containing tRNA, UDP-MurNAc-pentapeptide, and FemX. The LRMA, which is located in the centre of Paris, has up-to-date equipment for molecular biology, protein purification and crystallization, as well as good computing facilities. Scientists have access to the ESRF synchrotron facility (Grenoble, France). The candidate should preferentially be a biochemist (PhD) with a strong background in enzymology, but candidates with a PhD in organic chemistry or crystallography willing to acquire experience in biochemistry are also welcome to apply. Previous experience working with tRNA would be an advantage.

1. Mainardi, J.L., Villet R, Bugg T.D, Mayer C, Arthur M. 2008. Evolution of peptidoglycan synthesis under the selective pressure of antibiotics in Gram-positive bacteria. FEMS Microbiol. Rev. 32:386-408.

2. Bouhss, A., N. Josseaume, D. Allanic, M. Crouvoisier, L. Gutmann, JL. Mainardi, D. Mengin-Lecreulx, van J. Heijenoort, and M. Arthur. 2001. J. Bacteriol. 183:5122-5127.

3. Bouhss, A., N. Josseaume, A. Severin, K. Tabei, J.E. Hugonnet, D. Shlaes, D. Mengin-Lecreulx, J. van Heijenoort, and M. Arthur. 2002. J. Biol. Chem. 277:45935-45941.

4. Biarrotte-Sorin, S., AP. Maillard, J. Delettré, W. Sougakoff, D. Blanot, K. Blondeau, JE. Hugonnet, C. Mayer, and M. Arthur. 2003. Acta Crystallog. D. 59: 1055-1057.

5. Biarrotte-Sorin, S., AP. Maillard, J. Delettre, W. Sougakoff, M. Arthur, and C. Mayer. 2004. Structure. 12:2572-2567.

6. Maillard, A.P., S. Biarrotte-Sorin, R. Villet, S. Mesnage, A. Bouhss, W. Sougakoff, C. Mayer, and  M. Arthur. 2005. Structure-based site-directed mutagenesis of the UDP-MurNAc-pentapeptide-binding cavity of the FemX alanyl-transferase from Weissella viridescens . J. Bacteriol. 187:3833-3838.

7. Arbeloa, A., JE. Hugonnet, AC. Sentilhes, N. Josseaume, L. Dubost, C. Monsempes, D. Blanot, JP. Brouard, and M. Arthur. 2004. J Biol Chem. 279:41546-41556.

8. Magnet, S., A. Arbeloa, J.L. Mainardi, J.E. Hugonnet, M. Fourgeaud, L. Dubost, A. Marie, V. Delfosse, C. Mayer, L.B. Rice, and M. Arthur. 2007. Specificity of L,D-transpeptidases from Gram-positive bacteria producing different peptidoglycan chemotypes.  J. Biol. Chem. 282:13151-13159.

9. Villet, R., M. Fonvielle., P. Busca,, M. Chemama, A.P. Maillard, J.E. Hugonnet, L. Dubost, A. Marie, N. Josseaume, S. Mesnage, C. Mayer, J.M. Valéry, M. Ethève-Quelquejeu, and M. Arthur. 2007. Idiosyncratic features in tRNAs participating in bacterial cell wall synthesis. Nucl. Acids  Res. 35:6870-6883.

10. Chemama, M., M. Fonvielle, R. Villet, M. Arthur, J.M. Valéry, and M. Etheve-Quelquejeu. 2007. Stable analogues of aminoacyl-tRNA for inhibition of an essential step of bacterial cell wall synthesis. J. Am. Chem. Soc. 129:12642-12643.

Published May 26, 2008