– Hemopexin (HPX) serves as scavenger and transporter of toxic plasma heme to the liver. HPX is formed by two four-bladed beta-propeller domains, resembling two thick disks that lock together at a 90 degrees angle. The heme is bound between the two beta-propeller domains in a pocket formed by the interdomain linker peptide.HPX, acting not only as a heme carrier but also displaying transient heme-based ligand binding and (pseudo-)enzymatic properties, could be considered a ‘chronosteric’ heme-protein.