Metallothioneins are small proteins that have a high content of cysteine residues wich allow them to bind heavy metal ions through clusters of thiolate bonds. MymT binds up to seven ions of Cu(+), with a preference for four to six Cu(+) ions, in a solvent-shielded core. MymT protects M.tuberculosis from copper toxicity. Up-regulated by copper, cadmium, cobalt, nickel and zinc, but not manganese. Copper and cadmium salts afford the strongest metal-dependent induction at about 1,000-fold. Also highly up-regulated under conditions that are believed to be attained in phagosomes of interferon-gamma-activated macrophages, including production of nitric oxide and reactive oxygen intermediates, mild acid (pH 5.5), and cell wall perturbation (PubMed:18724363). Repressed by RicR (PubMed:21166899). Cells lacking this gene show hypersensitivity to Cu(+) toxicity but not to divalent heavy metals such as Zn(2+). Deficiency of MymT does not impair M.tuberculosis virulence in mice. NO and reactive nitrogen intermediates (RNI) can displace Cu(+) from MymT. Belongs to the metallothionein superfamily. It is uncertain whether Met-1 or Met-6 is the initiator. If Met-1 is the initiator, MymT would undergo a first cleavage after Arg-5 followed by processing of the N-terminal methionine.