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Please use this identifier to cite or link to this item: https://dspace.ffh.bg.ac.rs/handle/123456789/212
Title: Electronic structural flexibility of heterobimetallic Mn/Fe cofactors: R2lox and R2c proteins
Authors: Shafaat, Hannah S
Griese, Julia J
Pantazis, Dimitrios A
Roos, Katarina
Andersson, Charlotta S
Popović Bijelić, Ana 
Gräslund, Astrid
Siegbahn, Per E M
Neese, Frank
Lubitz, Wolfgang
Högbom, Martin
Cox, Nicholas
Issue Date: 24-Sep-2014
Journal: Journal of the American Chemical Society
Abstract: 
The electronic structure of the Mn/Fe cofactor identified in a new class of oxidases (R2lox) described by Andersson and Högbom [Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 5633] is reported. The R2lox protein is homologous to the small subunit of class Ic ribonucleotide reductase (R2c) but has a completely different in vivo function. Using multifrequency EPR and related pulse techniques, it is shown that the cofactor of R2lox represents an antiferromagnetically coupled Mn(III)/Fe(III) dimer linked by a μ-hydroxo/bis-μ-carboxylato bridging network. The Mn(III) ion is coordinated by a single water ligand. The R2lox cofactor is photoactive, converting into a second form (R2loxPhoto) upon visible illumination at cryogenic temperatures (77 K) that completely decays upon warming. This second, unstable form of the cofactor more closely resembles the Mn(III)/Fe(III) cofactor seen in R2c. It is shown that the two forms of the R2lox cofactor differ primarily in terms of the local site geometry and electronic state of the Mn(III) ion, as best evidenced by a reorientation of its unique (55)Mn hyperfine axis. Analysis of the metal hyperfine tensors in combination with density functional theory (DFT) calculations suggests that this change is triggered by deprotonation of the μ-hydroxo bridge. These results have important consequences for the mixed-metal R2c cofactor and the divergent chemistry R2lox and R2c perform.
URI: https://dspace.ffh.bg.ac.rs/handle/123456789/212
ISSN: 0002-7863
DOI: 10.1021/ja507435t
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University of Belgrade
Faculty of Physical Chemistry
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PAC 105305
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University of Belgrade Faculty of Physical Chemistry