Resonance Raman spectra of ferrochelatase reveal porphyrin distortion upon metal binding

Milton E. Blackwood, Thomas S. Rush, Amy Medlock, Harry A. Dailey, Thomas G. Spiro

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


Ferrochelatase catalyzes Fe2+ insertion into porphyrins, and is inhibited by Hg2+. Resonance Raman spectra of mesoporphyrin IX show that binding to ferrochelatase restricts the conformation of the propionate side chains, but does not perturb the ring conformation. However, a pronounced perturbation is seen in the ternary complex with Hg2+. Several additional RR bands are activated, including some arising from [R-active vibrations, establishing loss of an effective symmetry center. Out-of-plane modes appear in the low frequency region. The strongest of these bands, γ5 and γ6, correspond to pyrrole tilting vibrations, which are in the same symmetry class as a doming distortion of the porphyrin. All four pyrrole N atoms are pointing toward the same side of the porphyrin plane, a geometry expected to facilitate Fe2+ insertion. This distortion is proposed to result from occupation of a metal-binding site, proximate to the prophyrin, which promotes insertion of Fe2+, while occupation by Hg2+ is inhibitory.

Original languageEnglish (US)
Pages (from-to)12170-12174
Number of pages5
JournalJournal of the American Chemical Society
Issue number50
StatePublished - Dec 17 1997
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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