Structure of the Binuclear Iron Center in Hemerythrin by X-ray Absorption Spectroscopy

W. T. Elam, E. A. Stern, J. D. McCallum, J. Sanders-Loehr

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Abstract

Iron K-edge X-ray absorption data, including the near-edge structure and the extended X-ray absorption fine structure (EXAFS), have been measured for the respiratory protein hemerythrin in the biologically active oxy and deoxy forms of hemerythrin as well as metazido- and methydroxohemerythrin. The active-site structure is found to be very similar in the oxy and met forms, but distinctly different in deoxyhemerythrin. The binuclear iron center in oxy- and methemerythrins contains a μ-oxo bridge similar to Fe2O-containing standard compounds. The EXAFS data for metazidohemerythrin indicate that the average iron environment consists of a total of five nitrogen and oxygen ligands at 2.15 ± 0.05 Å and a bridging oxygen at 1.80 ± 0.08 Å, implying a bridging bond angle of 152 (+28/−13)0. Deoxyhemerythrin shows distinct changes in the first-shell EXAFS, and the iron-iron peak has disappeared, indicating loss of the μ-oxo bridge upon reduction.

Original languageEnglish
Pages (from-to)6369-6373
Number of pages5
JournalJournal of the American Chemical Society
Volume104
Issue number23
DOIs
StatePublished - 1982
Externally publishedYes

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