Mycobacterium tuberculosis tyrosine phosphatase A (PtpA) activity is modulated by S-nitrosylation.

M. tuberculosis PtpA and PtpB, the only two phosphotyrosine phosphatases (Ptps) present in this pathogen, play an important role in mycobacteria survival inside macrophages. The aim of the present work was to investigate M. tuberculosis PtpA and PtpB susceptibility to S-nitrosylation, a reversible covalent bond between nitric oxide (NO) and specific cysteine (sulfur) residues in proteins. PtpB was not modified by NO, in contrast, PtpA Cys53 was identified by site directed mutagenesis as the target of S-nitrosylation.