Molecular Genetics - CNRS URA2172  

  HEADProf. PUGSLEY Anthony /
Dr KREHENBRINK Martin / Dr RICHET Evelyne / Dr DANOT Olivier / GUILVOUT Ingrid
VIDAL-INGIGLIARDI Dominique / Dr KOLB Annie / Dr NOREL Françoise

  Annual Report

This unit comprises three groups, headed by Drs Kolb, Richet and Pugsley, whose aim is to understand the molecular details of basic processes such as transcription regulation and protein traffic in bacteria using biochemistry, structural biology and classical and molecular genetics.

Dr. Kolb’s group mainly studies the bacterial RNA polymerase stationary phase sigma factor S, the way is recognizes and binds to target DNA in its specific promoters, and the way its assembly into RNA polymerase is controlled and responds to growth phase and other factors. They have identified phenotypes diagnostic of sigma S dysfunction due to alterations in regulating factors. The group also studies anti-sigma factors, which affect sigma factor activity and help maintain the exquisite balance in RNA polymerase activity at different promoters

Dr. Richet’s group works on the transcription activator MalT, which responds to the presence of maltodextrins to stimulate the expression of genes required for their transport and metabolism in E. coli. MalT, the founder member of the STAND signal-transducing ATPases (STAND), comprises four domains responsible for DNA binding, ligand recognition, ATP hydrolysis and multimerization. MalT activation involves maltotriose binding and multimerization Inactive MalT binds as a monomer to negative effector proteins, including MalK, the ATPase component of the maltodextrin permease.

Dr. Pugsley’s group works on protein traffic and membrane assembly, mainly on the bacterial type II secretion system. Three of its 12 protein components are currently investigated. Secretin forms a dodecameric channel in the outer membrane to permit folded proteins to exit the cell from the periplasm. The second protein studied is a chaperone that prevents premature secretin oligomerization and ensures its correct localization. In its absence, secretin locates to the inner membrane, where it forms correctly assembled channels. The third protein of particular interest forms a periplasmic filament that resembles surface appendages called pili. Pseudopili probably promote secretion by cycles of assembly and disassembly that literally push the secreted protein through the secretin channel. Finally, this group also studies how this unique secretion system achieves exquisite selectivity (only one protein is secreted out of >150 proteins in the periplasm).

The Pugsley group also works on lipoprotein biogenesis and localization, and especially on the enzymes that link the fatty acids onto the 100–or–so lipoproteins made by E. coli. These enzymes are potential targets for antibacterial agents specific for Gram-negative bacteria.


3D projection map of secretin


Publications 2006 of the unit on Pasteur's references database

Activity Reports 2006 - Institut Pasteur
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