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Three Aromatic Residues are Required for Electron Transfer during Iron Mineralization in Bacterioferritin
Author(s) -
Bradley Justin M.,
Svistunenko Dimitri A.,
Lawson Tamara L.,
Hemmings Andrew M.,
Moore Geoffrey R.,
Le Brun Nick E.
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201507486
Subject(s) - chemistry , mineralization (soil science) , catalysis , photochemistry , electron transfer , ferric , electron transport chain , ceruloplasmin , metalloprotein , redox , cofactor , inorganic chemistry , organic chemistry , biochemistry , nitrogen , enzyme
Ferritins are iron storage proteins that overcome the problems of toxicity and poor bioavailability of iron by catalyzing iron oxidation and mineralization through the activity of a diiron ferroxidase site. Unlike in other ferritins, the oxidized di‐Fe 3+ site of Escherichia coli bacterioferritin (EcBFR) is stable and therefore does not function as a conduit for the transfer of Fe 3+ into the storage cavity, but instead acts as a true catalytic cofactor that cycles its oxidation state while driving Fe 2+ oxidation in the cavity. Herein, we demonstrate that EcBFR mineralization depends on three aromatic residues near the diiron site, Tyr25, Tyr58, and Trp133, and that a transient radical is formed on Tyr25. The data indicate that the aromatic residues, together with a previously identified inner surface iron site, promote mineralization by ensuring the simultaneous delivery of two electrons, derived from Fe 2+ oxidation in the BFR cavity, to the di‐ferric catalytic site for safe reduction of O 2 .