Mossbauer spectroscopy of Fe/S proteins

Iron-sulfur (Fe/S) clusters are structurally and functionally diverse cofactors that are found in all domains of life. Fe-57 Mossbauer spectroscopy is a technique that provides information about the chemical nature of all chemically distinct Fe species contained in a sample, such as Fe oxidation and spin state, nuclearity of a cluster with more than one metal ion, electron spin ground state of the cluster, and delocalization properties in mixed-valent clusters. Moreover, the technique allows for quantitation of all Fe species, when it is used in conjunction with electron paramagnetic resonance (EPR) spectroscopy and analytical methods. Fe-57-Mossbauer spectroscopy played a pivotal role in unraveling the electronic structures of the well-established [2Fe-2S](2+/+), [3Fe-4S](1+/0), and [4Fe-4S](3+/2+/1+/0) clusters and -more-recently- was used to characterize novel Fe/S clustsers, including the [4Fe-3S] cluster of the O-2-tolerant hydrogenase from Aquifex aeolicus and the 3Fe-cluster intermediate observed during the reaction of lipoyl synthase, a member of the radical SAM enzyme superfamily. (C) 2014 Elsevier B.V. All rights reserved.