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Ferric and Ferrous Iron in Nitroso‐Myoglobin: Computer Simulations of Stable and Metastable States and Their Infrared Spectra
Author(s) -
Nutt David R.,
Meuwly Markus
Publication year - 2007
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200600563
Subject(s) - myoglobin , ferrous , chemistry , ferric , crystallography , heme , hemeprotein , metastability , potential energy surface , inorganic chemistry , ab initio , computational chemistry , organic chemistry , enzyme
The binding of NO to iron is involved in the biological function of many heme proteins. Contrary to ligands like CO and O 2 , which only bind to ferrous (Fe II ) iron, NO binds to both ferrous and ferric (Fe III ) iron. In a particular protein, the natural oxidation state can therefore be expected to be tailored to the required function. Herein, we present an ab initio potential‐energy surface for ferric iron interacting with NO. This potential‐energy surface exhibits three minima corresponding to η 1 ‐NO coordination (the global minimum), η 1 ‐ON coordination and η 2 coordination. This contrasts with the potential‐energy surface for Fe II –NO, which exhibits only two minima (the η 2 coordination mode for Fe II is a transition state, not a minimum). In addition, the binding energies of NO are substantially larger for Fe III than for Fe II . We have performed molecular dynamics simulations for NO bound to ferric myoglobin (Mb III ) and compare these with results obtained for Mb II . Over the duration of our simulations (1.5 ns), all three binding modes are found to be stable at 200 K and transiently stable at 300 K, with eventual transformation to the η 1 ‐NO global‐minimum conformation. We discuss the implication of these results related to studies of rebinding processes in myoglobin.