| Popis: |
Summary The pathogenicity of mycobacteria is closely asso- ciated with their ability to export virulence factors. For this purpose, mycobacteria possess different protein secretion systems, including the acces- sory Sec translocation pathway, SecA2. Although this pathway is associated with intracellular sur- vival and virulence, the SecA2-dependent effector proteins remain largely undefined. In this work, we studied a Mycobacterium marinum secA2 mutant with an impaired capacity to initiate granuloma for- mation in zebrafish embryos. By comparing the proteomic profile of cell envelope fractions from the secA2 mutant with wild type M. marinum ,w e identified putative SecA2-dependent substrates. Immunoblotting procedures confirmed SecA2- dependent membrane localization for several of these proteins, including the virulence factor protein kinase G (PknG). Interestingly, pheno- typical defects of the secA2 mutant are similar to those described for ΔpknG, including phagosomal maturation. Overexpression of PknG in the secA2 mutant restored its localization to the cell enve- lope. Importantly, PknG-overexpression also par- tially restored the virulence of the secA2 mutant, as indicated by enhanced infectivity in zebrafish embryos and restored inhibition of phagosomal maturation. These results suggest that SecA2- dependent membrane localization of PknG is an important determinant for M. marinum virulence. |
