Auteur / Autrice : | Conghui You |
Direction : | Antoine Danchin |
Type : | Thèse de doctorat |
Discipline(s) : | Génétique cellulaire et moléculaire |
Date : | Soutenance en 2007 |
Etablissement(s) : | Versailles-St Quentin en Yvelines |
Mots clés
Résumé
In Bacillus subtilis, methionine aminopeptidases (MAP) and methionine sulfoxide reductases (MSR) maintain the methionine pool. Recycling of the initiation methionine of proteins is essential. Whereas most prokaryotes have a single MAP gene, B. Subtilis has two, mapA and mapB (yflG). MapB was 100-fold more efficient than MapA when assayed on some synthetic peptide substrates. Unlike MapA, MapB showed a strong preference for cobalt. They are both functional in vivo, and their gene products distribute evenly in the cell. The expression of mapA is 50 to 100-fold higher than that of mapB in vivo, which could explain why only mapA is the essential gene. Further phylogeny analysis suggests that the function of MapB might be associated to pathogenicity related activities. MSRs are widely studied for their repair role but not for their expression regulation. In B. Subtilis, MSR-coding genes (msrA and msrB) constitute an operon with a unique sigma A-dependent promoter. Their expression was induced specifically by paraquat (PQ) but not by H2O2. Spx, a global oxidative stress regulator, was implicated in the above process but partially. The function of Spx in the regulation depended on its CXXC motif. A genome-wide mutagenesis analysis identified a second gene, yjbH, participating in the expression regulation of this operon, possibly through controlling the amount of Spx in vivo. YjbH and Spx were shown to display direct protein-protein interaction. For the first time, our work uncovered several elements controlling the expression regulatory pathway of the msrAB operon in B. Subtilis, especially the PQ-specific oxidative induction pathway.