| Popis: |
The ATP-binding cassette (ABC) transporter systems are a conserved superfamily of multisubunit permeases that are found in all living organisms. Bacterial ABC transporters can be either importers or exporters. The ABC proteins form the largest paralogous family of proteins in Escherichia coli. It was initially predicted as a daunorubicin exporter on the basis of its similarity to the drrAB locus from Streptomyces peucetius. Transcriptome analysis of Mycobacterium tuberculosis expression in macrophages showed that 454 genes were induced and 147 genes were repressed in activated or resting macrophages at 24 hours compared with broth culture. In several bacteria, peptide transport can be important for nutrition of the cell, signaling processes such as regulation of gene expression, sporulation, chemotaxis, competence, and virulence. Phosphate is another essential anion that is also transported by one or several multisubunits ABC permeases in mycobacteria. The mkl gene has been shown to be required for macrophage survival and also has been identified twice as being essential for survival of M. tuberculosis in mice. The phosphate transport system (Pst) from M. tuberculosis is a tightly regulated high-affinity system encoded by three putative pst operons, suggesting that the bacteria are involved in subtle biochemical adaptations of M. tuberculosis for their survival under varying conditions during the infectious cycle. Active multidrug efflux pumps and the mycobacterial cell wall permeability barrier are the mechanisms that are thought to be potentially involved in the natural drug resistance of mycobacteria. |
