Human ferrochelatase is an iron-sulfur protein

Biochemistry. 1994 Jan 18;33(2):403-7. doi: 10.1021/bi00168a003.


Recombinant human ferrochelatase has been expressed in Escherichia coli and purified to homogeneity. Metal analyses revealed approximately 2 mol of non-heme Fe per mol of the purified enzyme (M(r) = 40,000). The UV-visible absorption spectrum of the purified enzyme consists of a protein absorption at 278 nm (epsilon approximately 90,000 M-1 cm-1) and bands at 330 nm (epsilon approximately 24,000 M-1 cm-1), 460 nm (shoulder, epsilon approximately 11,000 M-1 cm-1), and 550 nm (shoulder, epsilon approximately 9000 M-1 cm-1) that are indicative of a [2Fe-2S]2+ cluster. The spectra show an additional band at 415 nm that varied in intensity for different preparations and is attributed, at least in part, to a minor component of enzyme-associated high-spin Fe(III) heme. The presence of a single [2Fe-2S]2+,+ cluster as a redox active component of human ferrochelatase was confirmed by variable-temperature MCD and EPR studies of the dithionite-reduced enzyme which showed the presence of a S = 1/2 [2Fe-2S]+ cluster in addition to residual high spin Fe(II) heme. The reduced enzyme exhibits a S = 1/2 EPR signal, g = 2.00, 1.94, 1.91 accounting for 0.75 +/- 0.25 spins/molecule, that readily saturates at low microwave powers below 10 K but is observable without significant broadening at temperatures up to 100 K. The Fe-S cluster is labile and gradually disappears over period of 24 h, with concomitant loss of enzyme activity, when the enzyme is stored aerobically at 4 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Circular Dichroism
  • Dithionite
  • Electron Spin Resonance Spectroscopy
  • Escherichia coli / enzymology
  • Ferrochelatase / chemistry*
  • Ferrochelatase / metabolism
  • Humans
  • Iron-Sulfur Proteins / chemistry*
  • Iron-Sulfur Proteins / metabolism
  • Molecular Sequence Data
  • Oxidation-Reduction
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae / enzymology
  • Spectrophotometry, Ultraviolet
  • Structure-Activity Relationship


  • Iron-Sulfur Proteins
  • Recombinant Proteins
  • Dithionite
  • Ferrochelatase