The heme-iron geometry of ferrous nitrosylated heme-serum lipoproteins, hemopexin, and albumin: A comparative EPR study

Mauro Fasano, Marco Mattu, Massimo Coletta, Paolo Ascenzi

Research output: Contribution to journalArticlepeer-review

Abstract

Serum high and low density lipoproteins, albumin, and hemopexin (HDL, LDL, SA, and HPX, respectively) serve as traps of toxic plasma heme and participate in its complete clearance by transportation to the liver. Moreover, SA-(heme) and HPX-heme have been proposed to facilitate NO scavenging in vivo. Here, the EPR-spectroscopic properties of ferrous nitrosylated heme-human high and low density lipoproteins (HDL-heme-NO and LDL-heme-NO, respectively) as well as of ferrous nitrosylated heme-rabbit serum hemopexin (HPX-heme-NO) are reported and analyzed in parallel with those of ferrous nitrosylated heme-human serum albumin (SA-heme-NO). HDL-heme-NO and LDL-heme-NO as well as SA-heme-NO, in the absence of allosteric effectors (i.e., N-form), are five-coordinate heme-iron species, characterized by the three-line splitting observed in the high magnetic field region of the X-band EPR spectrum. On the other hand, SA-heme-NO, in the presence of drugs (i.e., B-form), and HPX-heme-NO are six-coordinate heme-iron species, characterized by an X-band EPR spectrum with an axial geometry. The heme-iron coordination state of HDL-heme-NO, LDL-heme-NO, SA-heme-NO, and HPX-heme-NO is in keeping with values of ferric heme dissociation rate constants which decrease in the following order: LDL>HDL>SA>HPX. Altogether, these observations suggest that HPX displays a cleft much more suitable for heme binding than other heme-carriers.

Original languageEnglish
Pages (from-to)487-490
Number of pages4
JournalJournal of Inorganic Biochemistry
Volume91
Issue number3
DOIs
Publication statusPublished - Aug 30 2002

Keywords

  • EPR spectroscopic properties
  • Ferrous nitrosylated heme-serum proteins
  • Heme-human albumin
  • Heme-human lipoproteins
  • Heme-iron geometry
  • Heme-rabbit hemopexin

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry

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