5'-Adenosinephosphosulphate reductase (CysH) protects Mycobacterium tuberculosis against free radicals during chronic infection phase in mice

Mol Microbiol. 2006 Mar;59(6):1744-53. doi: 10.1111/j.1365-2958.2006.05075.x.


A major obstacle to tuberculosis (TB) control is the problem of chronic TB infection (CTBI). Here we report that 5'-adenosinephosphosulphate reductase (CysH), an enzyme essential for the production of reduced-sulphur-containing metabolites, is critical for Mycobacterium tuberculosis (Mtb) survival in chronic infection phase in mice. Disruption of cysH rendered Mtb auxotrophic for cysteine and methionine, and attenuated virulence in BALB/c and C57BL/6 immunocompetent mice. The mutant and wild-type Mtb replicated similarly during the acute phase of infection, but the mutant showed reduced viability during the persistent phase of the infection. The cysH mutant caused disease and death after 4-7 weeks of infection in four different groups of mice - Rag1(-/-), NOS2(-/-), gp91phox(-/-) NOS2(-/-) and gp91phox(-/-) mice given aminoguanidine [to suppress the effects of nitric oxide synthase 2 (NOS2)]- indicating minimal metabolic effect on the cysH mutant survival in these mice. The cysH mutant was also susceptible to peroxynitrite and hydrogen peroxide in vitro. These results show that CysH is important for Mtb protection during the chronic infection phase, and that resistance to nitrosative and oxidative stress may be the mechanism of this protection. Thus, this metabolic gene of an intracellular pathogen could have a secondary role in protection against the host immune response. Finally the lack of an endogenous human orthologue of cysH and its possible role in defence against adaptive immunity renders CysH an attractive enzyme for further studies as a target for therapeutics active against CTBI.

MeSH terms

  • Animals
  • Bacterial Proteins / genetics
  • Bacterial Proteins / physiology*
  • Chronic Disease
  • Cysteine / metabolism
  • Enzyme Inhibitors / pharmacology
  • Free Radicals / metabolism*
  • Free Radicals / pharmacology
  • Genes, Bacterial
  • Guanidines / pharmacology
  • Lung / microbiology
  • Lung / pathology
  • Methionine / metabolism
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Mice, Mutant Strains
  • Mutation
  • Mycobacterium tuberculosis / drug effects
  • Mycobacterium tuberculosis / enzymology*
  • Mycobacterium tuberculosis / pathogenicity*
  • Nitric Oxide Synthase Type II / antagonists & inhibitors
  • Oxidative Stress
  • Oxidoreductases Acting on Sulfur Group Donors / genetics
  • Oxidoreductases Acting on Sulfur Group Donors / physiology*
  • Tuberculosis, Pulmonary / genetics
  • Tuberculosis, Pulmonary / microbiology*
  • Tuberculosis, Pulmonary / pathology


  • Bacterial Proteins
  • Enzyme Inhibitors
  • Free Radicals
  • Guanidines
  • Methionine
  • Nitric Oxide Synthase Type II
  • Nos2 protein, mouse
  • Oxidoreductases Acting on Sulfur Group Donors
  • adenylylsulfate reductase
  • Cysteine
  • pimagedine