Heme-binding protein able to scavenge peroxynitrite and to protect free L-tyrosine against peroxynitrite-mediated nitration, by acting as a peroxynitrite isomerase that converts peroxynitrite to nitrate. Therefore, this protein likely plays a role in peroxynitrite sensing and in the detoxification of reactive nitrogen and oxygen species (RNS and ROS, respectively). Is able to bind nitric oxide (NO) in vitro, but may act as a sensor of peroxynitrite levels in vivo, possibly modulating the transcriptional activity residing in the N-terminal region. peroxynitrite = nitrate Binds 1 heme b group per subunit, that coordinates a highly solvent-exposed Fe(III) atom. Nitrogen metabolism. Homodimer. Localizes mainly in the cytoplasm and partially in the nucleus. The C-terminal nitrobindin region coordinates a heme and bears the isomerase activity. The N-terminal zinc finger domain likely binds DNA and may be involved in transcriptional regulation. In the C-terminal section; belongs to the nitrobindin family. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus.