Biography
Biography: Meriem El Ghachi
Abstract
Undecaprenyl-phosphate C55-P is a key lipid carrier of glycan intermediate required for the synthesis of a variety of cell wall polymers such as Peptidoglycan (PG), Lipopolysaccharides (LPS) O-antigen wall teichoic acids, capsular polysaccharide, common enterobacterial antigen, membrane-derivative oligosaccharides and exopolysaccharides. In bacteria, during peptidoglycan synthesis, the phospho-N-acetylmuramoyl (-pentapeptide) -N-acetyl glucosamine is the essential motif carried by the C55-P. The resulting lipid, C55-PP-MurNAc-(pentatpetide)-GlucNAc (lipid II), is translocated towards the periplasmic side by several putative flippases. The MurNAc-(pentatpetide)-GlucNAc is added to the elongating chains of PG and C55- P is released as C55- PP. This precursor is also provided by the de novo synthesis in the cytosol that is catalyzed by a Cis-Prenyl Pyrophosphate Synthase, UPPS, which successively adds eight isoprene units from C5-PP on farnesyl pyrophosphate. Two families of phosphatases can perform the subsequent dephosphorylation of C55-PP into C55-P, common to the in vitro synthesis and carrier lipid recycling. In E. coli, 1 BacA and 3 phosphatidic acid phosphatases 2 (PgpB, YbjG and LpxT), active on C55-PP have been identified. PgpB being also involved in the phosphatidyl glycerol metabolism and LpxT transferring the phosphate from C55-PP to lipid A. Whereas Bacillus subtilis has three C55-PP phosphatases 1 BacA (YubB) and 2 phosphatidic acid phosphatases 2 (YwoA and YodM). We obtained the structure of BacA using lipidic cubic phase method. The crystal structure at 2.6 A revealed an unexpected fold according to the previous biochemical studies. Moreover, we solved the structure of bsPgpB (yodM) in the presence and absence of its favorite substrate, phosphatidyl glycerol.