S-nitroso proteome of Mycobacterium tuberculosis: Enzymes of intermediary metabolism and antioxidant defense
Reactive Nitrogen Species
The immune response to Mycobacterium tuberculosis (Mtb) includes expression of nitric oxide (NO) synthase (NOS)2, whose products can kill Mtb in vitro with a molar potency greater than that of many conventional antitubercular agents. However, the targets of reactive nitrogen intermediates (RNIs) in Mtb are unknown. One major action of RNIs is protein S-nitrosylation. Here, we describe, to our knowledge, the first proteomic analysis of S-nitrosylation in a whole organism after treating Mtb with bactericidal concentrations of RNIs. The 29 S-nitroso proteins identified are all enzymes, mostly serving intermediary metabolism, lipid metabolism, and/or antioxidant defense. Many are essential or implicated in virulence, including defense against RNIs. For each of two target enzymes tested, lipoamide dehydrogenase and mycobacterial proteasome ATPase, S-nitrosylation caused enzyme inhibition. Moreover, endogenously biotinylated proteins were driven into mixed disulfide complexes. Targeting of metabolic enzymes and antioxidant defenses by means of protein S-nitrosylation and mixed disulfide bonding may contribute to the antimycobacterial actions of RNIs.