A new dehydratase conferring innate resistance to thiacetazone and intra-amoebal survival of Mycobacterium smegmatis

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

  • Séverine Carrère-Kremer, INSERM
  • ,
  • Mickael Blaise, Centre d'étude des Pathogènes pour la Biotechnologie et la Santé (CPBS), Centre for Carbohydrate Recognition and Signalling, Department of Molecular Biology and Genetics, Aarhus University
  • ,
  • Vipul K. Singh, Universite de Montpellier
  • ,
  • Laeticia Alibaud, Universite de Montpellier
  • ,
  • Edouard Tuaillon, INSERM
  • ,
  • Iman Halloum, CNRS FRE3689
  • ,
  • Robert van de Weerd, VU University Medical Center
  • ,
  • Yann Guérardel, Université des Sciences et Technologies de Lille 1
  • ,
  • Michel Drancourt, Université Aix-Marseille
  • ,
  • Howard Takiff, IVIC
  • ,
  • Jeroen Geurtsen, Crucell Holland BV
  • ,
  • Laurent Kremer, CNRS FRE3689

Nontuberculous mycobacteria are innately resistant to most antibiotics, although the mechanisms responsible for their drug resistance remain poorly understood. They are particularly refractory to thiacetazone (TAC), a second-line antitubercular drug. Herein, we identified MSMEG_6754 as essential for the innate resistance of Mycobacterium smegmatis to TAC. Transposon-mediated and targeted disruption of MSMEG_6754 resulted in hypersusceptibility to TAC. Conversely, introduction of MSMEG_6754 into Mycobacterium tuberculosis increased resistance 100-fold. Resolution of the crystal structure of MSMEG_6754 revealed a homodimer in which each monomer comprises two hot-dog domains characteristic of dehydratase-like proteins and very similar to the HadAB complex involved in mycolic acid biosynthesis. Gene inactivation of the essential hadB dehydratase could be achieved in M.smegmatis and M.tuberculosis only when the strains carried an integrated copy of MSMEG_6754, supporting the idea that MSMEG_6754 and HadB share redundant dehydratase activity. Using M.smegmatis-Acanthamoeba co-cultures, we found that intra-amoebal growth of the MSMEG_6754 deleted strain was significantly reduced compared with the parental strain. This in vivo growth defect was fully restored upon complementation with catalytically active MSMEG_6754 or HadABC, indicating that MSMEG_6754 plays a critical role in the survival of M.smegmatis within the environmental host. MSMEG_6754 is responsible for the natural resistance of Mycobacterium smegmatis to the antitubercular drug thiacetazone. The crystal structure of the protein is very close to the one of the HadAB dehydratase involved in mycolic acid biosynthesis. We also demonstrate that MSMEG_6754 is a crucial determinant for intramoebal growth of M. smegmatis.

Original languageEnglish
JournalMolecular Microbiology
Volume96
Issue5
Pages (from-to)1085-1102
Number of pages18
ISSN0950-382X
DOIs
Publication statusPublished - 2015

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