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MitoNEET is a uniquely folded 2Fe 2S outer mitochondrial membrane protein stabilized by pioglitazone.

ABSTRACT: Iron-sulfur (Fe-S) proteins are key players in vital processes involving energy homeostasis and metabolism from the simplest to most complex organisms. We report a 1.5 A x-ray crystal structure of the first identified outer mitochondrial membrane Fe-S protein, mitoNEET. Two protomers intertwine to form a unique dimeric structure that constitutes a new fold to not only the approximately 650 reported Fe-S protein structures but also to all known proteins. We name this motif the NEET fold. The protomers form a two-domain structure: a beta-cap domain and a cluster-binding domain that coordinates two acid-labile 2Fe-2S clusters. Binding of pioglitazone, an insulin-sensitizing thiazolidinedione used in the treatment of type 2 diabetes, stabilizes the protein against 2Fe-2S cluster release. The biophysical properties of mitoNEET suggest that it may participate in a redox-sensitive signaling and/or in Fe-S cluster transfer.

SUBMITTER: Paddock ML

PROVIDER: S-EPMC1963346 | biostudies-literature | 2007 Sep

REPOSITORIES: biostudies-literature

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MitoNEET is a uniquely folded 2Fe 2S outer mitochondrial membrane protein stabilized by pioglitazone.

Paddock Mark L ML Wiley Sandra E SE Axelrod Herbert L HL Cohen Aina E AE Roy Melinda M Abresch Edward C EC Capraro Dominique D Murphy Anne N AN Nechushtai Rachel R Dixon Jack E JE Jennings Patricia A PA

Proceedings of the National Academy of Sciences of the United States of America 20070831 36

Iron-sulfur (Fe-S) proteins are key players in vital processes involving energy homeostasis and metabolism from the simplest to most complex organisms. We report a 1.5 A x-ray crystal structure of the first identified outer mitochondrial membrane Fe-S protein, mitoNEET. Two protomers intertwine to form a unique dimeric structure that constitutes a new fold to not only the approximately 650 reported Fe-S protein structures but also to all known proteins. We name this motif the NEET fold. The prot ...[more]

PMID: 17766440

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Project description:Human mitoNEET is a homodimeric iron-sulfur protein located in the outer mitochondrial membrane with unknown function, but which is known to interact with thiazolidinedione diabetes drugs. Each monomer houses a [2Fe-2S] cluster with an unusual (Cys)(3)(His)(1) ligation. The His ligand is important for enabling cluster release and for tuning the redox potential. We use multifrequency (X-, Ka-, and Q-band) and multitechnique (continuous-wave, electron spin-echo envelope modulation (ESEEM), pulsed electron-nuclear double resonance (ENDOR), and hyperfine sublevel correlation (HYSCORE)) electron paramagnetic resonance spectroscopy to investigate the cluster in its paramagnetic reduced [Fe(2+)Fe(3+)] (S = 1/2) state. It has a rhombic g tensor (2.007, 1.937, 1.897) with an average g value of 1.947 that falls between those of Rieske-type and ferredoxin-type [2Fe-2S] clusters. Simulation and least-squares fitting of orientation-selective Ka- and Q-band ENDOR, 1D ESEEM, and HYSCORE spectra of (14)N and (15)N-labeled mitoNEET yield the principal values and orientations of both the hyperfine tensor ((14)N, A(iso) = -6.25 MHz, T = -0.94 MHz) and the quadrupolar tensor (e(2)Qq/h = -2.47 MHz, eta = 0.38) of the ligating histidine nitrogen N(delta). From these, we can infer the absolute g tensor orientation with respect to the cluster: The g(2) axis is close to perpendicular to the [2Fe-2S] plane, and g(1) and g(3) are in-plane, but skewed from the Fe-Fe and S-S axes. In X-band ENDOR and ESEEM spectra, a weakly coupled nitrogen is visible, most likely the N(epsilon) of the histidine in the protonated state. We find that the cluster is in a valence-localized state, where Fe(2+) is His-bound. The field-sweep spectra show evidence of intercluster dipolar coupling that can be simulated using an uncoupled spin model for each cluster (S(Fe(2+)) = 2, S(Fe(3+)) = 5/2). The parameters determined in this work can function as reporters on how the cluster structure is altered upon pH changes and drug binding.

Dataset Information

MitoNEET is a uniquely folded 2Fe 2S outer mitochondrial membrane protein stabilized by pioglitazone.

Publications

MitoNEET is a uniquely folded 2Fe 2S outer mitochondrial membrane protein stabilized by pioglitazone.

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