Hemerythrin (Hr) like domains have the same four alpha helix bundle and a similar, but slightly different active site structure than hemerythrin. They are non-heme diiron binding proteins mainly found in bacteria and eukaryotes. Like Hr, they may be involved in oxygen transport or like human FBXL5 (F-box and leucine-rich repeat protein 5), a member of this group, play a role in cellular iron homeostasis.
Jiyao W et al.(2023). "The conserved domain database in 2023.",