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. 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. Was identified as a high-confidence drug target. Belongs to the nitrobindin family.