J. Biol. Chem., Vol. 258, Issue 4, 2115-2117, Feb, 1983
Semi-met oxidation level of chalcogenide derivatives of methemerythrin. Mossbauer and EPR studies
DM Kurtz Jr, JT Sage, M Hendrich, PG Debrunner and GS Lukat
Conclusive evidence is presented for an S = 1/2 spincoupled pair of high
spin ferric and ferrous ions in the major reaction product of sulfide with
the met form of the non-heme iron oxygen-carrying protein hemerythrin.
Evidence for an analogous selenide derivative is also reported. Mossbauer
and EPR spectroscopy establish (a) the charge and spin states of the
individual iron atoms in sulfidehemerythrin as Fe(III), S = 5/2, and
Fe(II), S = 2, and (b) the existence of an antiferromagnetic exchange
interaction that couples the two spins to a resultant spin S = 1/2. The
combined Mossbauer and EPR data confirm the correctness of the formulation
first proposed for semi-methemerythrin by Harrington, P.C., de Waal,
D.J.A., and Wilkins, R.G. ((1978) Arch. Biochem. Biophys. 191, 444-451) and
furthermore show that a majority of the iron centers in the protein can be
stabilized at this oxidation level. The results also demonstrate a new
route to semi-methemerythrin. A titration of methemerythrin with selenide
indicates that this derivative forms by a two step process consisting of
first, reduction to the semi-met oxidation level by selenide and second,
binding of selenide to either one or both irons.
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