A π-Helix Switch Selective for Porphyrin Deprotonation and Product Release in Human Ferrochelatase

Amy E. Medlock, Tamara A. Dailey, Teresa A. Ross, Harry A. Dailey, William N. Lanzilotta

Research output: Contribution to journalArticlepeer-review

53 Scopus citations


Ferrochelatase (protoheme ferrolyase, EC is the terminal enzyme in heme biosynthesis and catalyzes the insertion of ferrous iron into protoporphyrin IX to form protoheme IX (heme). Due to the many critical roles of heme, synthesis of heme is required by the vast majority of organisms. Despite significant investigation of both the microbial and eukaryotic enzyme, details of metal chelation remain unidentified. Here we present the first structure of the wild-type human enzyme, a lead-inhibited intermediate of the wild-type enzyme with bound metallated porphyrin macrocycle, the product bound form of the enzyme, and a higher resolution model for the substrate-bound form of the E343K variant. These data paint a picture of an enzyme that undergoes significant changes in secondary structure during the catalytic cycle. The role that these structural alterations play in overall catalysis and potential protein-protein interactions with other proteins, as well as the possible molecular basis for these changes, is discussed. The atomic details and structural rearrangements presented herein significantly advance our understanding of the substrate binding mode of ferrochelatase and reveal new conformational changes in a structurally conserved π-helix that is predicted to have a central role in product release.

Original languageEnglish (US)
Pages (from-to)1006-1016
Number of pages11
JournalJournal of Molecular Biology
Issue number4
StatePublished - Nov 2 2007
Externally publishedYes


  • X-ray crystallography
  • ferrochelatase
  • heme synthesis
  • protoporphyrin IX

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


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