Abstract
Hemopexin (HPX) serves as scavenger and transporter of toxic plasma heme to the liver. HPX is formed by two four-bladed β-propeller domains, resembling two thick disks that lock together at a 90° angle. The heme is bound between the two β-propeller domains in a pocket formed by the interdomain linker peptide. Residues His213 and His266 coordinate the heme iron atom giving a stable bis-histidyl complex. The HPX-heme geometry is reminiscent of heme-proteins endowed with ligand binding and (pseudo-)enzymatic properties. HPX-heme binds reversibly CO, •NO, and cyanide by detaching His213; however, O2 induces HPX-heme(II) oxidation. Furthermore, HPX-heme(II) facilitates •NO/O2 and •NO/peroxynitrite scavenging. Heme sequestering by HPX prevents heme-mediated activation of oxidants which induce the low-density lipoprotein oxidation. Here, ligand binding and (pseudo-)enzymatic properties of HPX-heme are reviewed. 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.
Original language | English |
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Pages (from-to) | 700-708 |
Number of pages | 9 |
Journal | IUBMB Life |
Volume | 59 |
Issue number | 11 |
DOIs | |
Publication status | Published - 2007 |
Keywords
- (pseudo-)enzymatic properties
- Heme-hemopexin
- Hemopexin
- Ligand binding properties
ASJC Scopus subject areas
- Biochemistry
- Molecular Biology
- Genetics
- Cell Biology