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) (PubMed:32295384). Is able to bind nitric oxide (NO) in vitro, but may act as a sensor of peroxynitrite levels in vivo (PubMed:32295384, PubMed:19938152). peroxynitrite = nitrate Binds 1 heme b group per subunit, that coordinates a highly solvent-exposed Fe(III) atom. Nitrogen metabolism. Homodimer. Forms a 10-stranded antiparallel beta-barrel structure able to accommodate a hydrophobic ligand in its interior. In fact, this fold hosts the heme group, which is located in a wide surface cleft. Belongs to the nitrobindin family.