Heme-hemopexin: a 'chronosteric' heme-protein

IUBMB Life. 2007 Nov;59(11):700-8. doi: 10.1080/15216540701689666.

Abstract

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. 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, O(2) induces HPX-heme(II) oxidation. Furthermore, HPX-heme(II) facilitates (*)NO/O(2) 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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Binding Sites
  • Carbon Monoxide / metabolism
  • Heme / chemistry*
  • Heme / metabolism
  • Hemopexin / chemistry*
  • Hemopexin / metabolism
  • Models, Molecular
  • Nitric Oxide / metabolism
  • Oxidation-Reduction
  • Oxygen / metabolism
  • Protein Binding
  • Protein Structure, Tertiary*

Substances

  • Nitric Oxide
  • Heme
  • Carbon Monoxide
  • Hemopexin
  • Oxygen