title: Role of P27 -P55 operon from Mycobacterium tuberculosis in the resistance to toxic compounds.
abstract: BACKGROUND
  The P27-P55 (lprG-Rv1410c) operon is crucial for the survival of Mycobacterium tuberculosis, the causative agent of human tuberculosis, during infection in mice. P55 encodes an efflux pump that has been shown to provide Mycobacterium smegmatis and Mycobacterium bovis BCG with resistance to several drugs, while P27 encodes a mannosylated glycoprotein previously described as an antigen that modulates the immune response against mycobacteria. The objective of this study was to determine the individual contribution of the proteins encoded in the P27-P55 operon to the resistance to toxic compounds and to the cell wall integrity of M. tuberculosis.
  
  
  METHODS
  In order to test the susceptibility of a mutant of M. tuberculosis H37Rv in the P27-P55 operon to malachite green, sodium dodecyl sulfate, ethidium bromide, and first-line antituberculosis drugs, this strain together with the wild type strain and a set of complemented strains were cultivated in the presence and in the absence of these drugs. In addition, the malachite green decolorization rate of each strain was obtained from decolorization curves of malachite green in PBS containing bacterial suspensions.
  
  
  RESULTS
  The mutant strain decolorized malachite green faster than the wild type strain and was hypersensitive to both malachite green and ethidium bromide, and more susceptible to the first-line antituberculosis drugs: isoniazid and ethambutol. The pump inhibitor reserpine reversed M. tuberculosis resistance to ethidium bromide. These results suggest that P27-P55 functions through an efflux-pump like mechanism. In addition, deletion of the P27-P55 operon made M. tuberculosis susceptible to sodium dodecyl sulfate, suggesting that the lack of both proteins causes alterations in the cell wall permeability of the bacterium. Importantly, both P27 and P55 are required to restore the wild type phenotypes in the mutant.
  
  
  CONCLUSIONS
  The results clearly indicate that P27 and P55 are functionally connected in processes that involve the preservation of the cell wall and the transport of toxic compounds away from the cells.
authors.affiliation: Instituto de Biotecnología, CICVyA-INTA, N, Repetto and De los Reseros, Buenos Aires, Argentina.
authors.forename: María V
authors.initials: MV
authors.lastname: Bianco
authors.forename: Federico C
authors.initials: FC
authors.lastname: Blanco
authors.forename: Belén
authors.initials: B
authors.lastname: Imperiale
authors.forename: Marina A
authors.initials: MA
authors.lastname: Forrellad
authors.forename: Roxana V
authors.initials: RV
authors.lastname: Rocha
authors.forename: Laura I
authors.initials: LI
authors.lastname: Klepp
authors.forename: Angel A
authors.initials: AA
authors.lastname: Cataldi
authors.forename: Nora
authors.initials: N
authors.lastname: Morcillo
authors.forename: Fabiana
authors.initials: F
authors.lastname: Bigi
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D015153:Blotting, Western; D002462:Cell Membrane / Q000737:chemistry; D002470:Cell Survival / Q000187:drug effects; D002473:Cell Wall / Q000737:chemistry; D004352:Drug Resistance, Microbial; D004591:Electrophoresis, Polyacrylamide Gel; D004977:Ethambutol / Q000494:pharmacology; D004996:Ethidium / Q000494:pharmacology; D007538:Isoniazid / Q000494:pharmacology; D008074:Lipoproteins / Q000235:genetics*; D026901:Membrane Transport Proteins / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000235:genetics*; D009876:Operon; D012394:Rosaniline Dyes / Q000494:pharmacology; D012967:Sodium Dodecyl Sulfate
chemical_list: D000890:Anti-Infective Agents; D001426:Bacterial Proteins; D008074:Lipoproteins; D026901:Membrane Transport Proteins; C110121:P27 protein, Mycobacterium; C425143:P55 protein, Mycobacterium; D012394:Rosaniline Dyes; C005095:malachite green; D012967:Sodium Dodecyl Sulfate; D004977:Ethambutol; D004996:Ethidium; D007538:Isoniazid