<sup>15</sup>N HYSCORE Characterization of the Fully Deprotonated, Reduced Form of the Archaeal Rieske [2Fe−2S] Center

Iwasaki, Toshio; Kounosu, Asako; Samoilova, Rimma I.; Dikanov, Sergei A.

doi:10.1021/ja0562393

Cited by 14 publications

(30 citation statements)

References 24 publications

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“…In the (ϩϪ) quadrant, two pairs of cross-peaks with a contour parallel to the diagonal are detected that have been attributed to the two coordinated 15 N ␦ 1,2 with the hyperfine splittings of the order of 6 and 8 MHz (25). The contour line shape analysis of these features recorded at different field positions (33,34) gave values for the hyperfine tensors in the axial approximation of a ϭ 6.6 and T ϭ 1.6 MHz for N ␦ 1 and of a ϭ 7.6 MHz and T ϭ 1.5 MHz for N ␦ 2 in 15 N-ISF. These tensors are very similar to those reported for other Rieske-type proteins obtained by orientation-selected 15 N Q-band electron nuclear double resonance (16) and 15 N HYSCORE (25).…”

Section: Resultsmentioning

confidence: 95%

“…Thus, the ratio ϳ20 between hyperfine couplings of the N ␦ and N ⑀ applies to the coordinated imidazoles in the Rieske cluster. This stability probably reflects the analogous mechanism of spin density transfer from the metal over the imidazole ring to the N ⑀ , which is also sensitive to protonation state (34). In view of this result, it would be interesting to study the N ⑀ hyperfine couplings for the Rieske cluster in the bc 1 complex to explore the interaction of ISP with occupants of the Q o site via the H-bond with the N ⑀ -H of one of the histidine ligands.…”

Section: Assignment Of the Frequencies In S-band Spectra-linesmentioning

confidence: 93%

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Identification of Hydrogen Bonds to the Rieske Cluster through the Weakly Coupled Nitrogens Detected by Electron Spin Echo Envelope Modulation Spectroscopy

Dikanov

Kolling

Endeward

et al. 2006

Journal of Biological Chemistry

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Proteins containing Rieske-type [2Fe-2S] clusters with two histidyl and two cysteinyl ligands play important roles in many biological electron transfer reactions such as aerobic respiration, photosynthesis, and biodegradation of various alkene and aromatic compounds. The distinct biological functions of this protein family are in part associated with the cluster redox potential and the pK of the oxidized form, which are roughly correlated with the number of hydrogen bonds from protein side chains and the peptide backbone to the cluster and its immediate ligands (1-6).In the cytochrome bc 1 /b 6f family, a Rieske iron-sulfur protein (ISP) 4 is a constituent of the high potential electron transfer chain that accepts the first electron in the bifurcated reaction at the ubihydroquinone (quinol, QH 2 ) oxidizing Q o site. In the catalytic mechanism at the Q o site, the redox reaction involves extraction of both an electron and a proton from the bound quinol and their transfer to the ISP through a short pathway that includes the ISP His-161 ring and the H-bond between N ⑀ and the -OH of the quinol substrate (7). It has been proposed that the electron transfer is gated by the low probability of finding the H-atom of the H-bond in the kinetically favorable position, determined by the pK difference between the quinol and the oxidized ISP (ISP ox ) (reviewed in Refs. 5 and 6). The pK on ISP ox is contributed by one of the cluster ligands, His-161 in bovine numbering, and is associated with H ϩ dissociation from the N ⑀ involved in the H-bond. The gating accounts for the fact that this first electron transfer is slower by more than 3 orders of magnitude than would be expected from the short distance (ϳ7 Å) involved (6, 7). The first electron transfer is the ratedetermining step in quinol oxidation under conditions of substrate saturation. Rate determination at this reaction is demonstrated by the fact that the overall rate depends on its driving force in a classical Marcus fashion, as shown through use of mutants of the ISP with modified redox potential (6 -13). Briefly, the driving force, ⌬G o , for the first electron transfer is determined by the redox potential difference between the donor (SQ/QH 2 ) and acceptor (ISP ox /ISPH) couples. Assuming that mutations in the ISP do not change E m (SQ/QH 2 ), a change in * This work was supported by National Institutes of Health Grants GM 35438 (to A. R. C.) and GM 62954 (to S. A. D.), Fogarty Grant PHS 1 RO3 TW 01495 (to A. R. C. and R. I. S.), and National Institutes of Health/National Center for Research Resources Grant S10-RR15878 for instrumentation. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 To whom correspondence may be addressed. E-mail: dikanov@uiuc.edu. 2 Present address: Dept. of Chemistry, Princeton University, Princeton, NJ 08540. 3 To whom correspondence may be addressed. E-mail:...

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Section: Resultsmentioning

confidence: 95%

Section: Assignment Of the Frequencies In S-band Spectra-linesmentioning

confidence: 93%

Identification of Hydrogen Bonds to the Rieske Cluster through the Weakly Coupled Nitrogens Detected by Electron Spin Echo Envelope Modulation Spectroscopy

Dikanov

Kolling

Endeward

et al. 2006

Journal of Biological Chemistry

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“…1c). Analysis of the 1D- and 2D-ESEEM spectra of reduced Rieske clusters from 14 N and 15 N nuclei has been previously performed38,41-44,48-51 and is not in the scope of the present work.…”

Section: Resultsmentioning

confidence: 99%

Proton Environment of Reduced Rieske Iron−Sulfur Cluster Probed by Two-Dimensional ESEEM Spectroscopy

et al. 2008

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The proton environment of the reduced [2Fe-2S] cluster in the water-soluble head domain of the Rieske iron-sulfur protein (ISF) from the cytochrome bc 1 complex of Rhodobacter sphaeroides has been studied by orientation-selected X-band 2D ESEEM. The 2D spectra show multiple crosspeaks from protons, with considerable overlap. Samples in which 1 H 2 O water was replaced by 2 H 2 O were used to determine which of the observed peaks belong to exchangeable protons, likely involved in hydrogen bonds in the neighborhood of the cluster. By correlating the cross-peaks from 2D spectra recorded at different parts of the EPR spectrum, lines from nine distinct proton signals were identified. Assignment of the proton signals was based on a point-dipole model for interaction with electrons of Fe(III) and Fe(II) ions, using the high-resolution structure of ISF from Rb. sphaeroides. Analysis of experimental and calculated tensors has led us to conclude that even 2D spectra do not completely resolve all contributions from nearby protons. Particularly, the seven resolved signals from non-exchangeable protons could be produced by at least thirteen protons. The contributions from exchangeable protons were resolved by difference spectra ( 1 H 2 O minus 2 H 2 O), and assigned to two groups of protons with distinct anisotropic hyperfine values. The largest measured coupling exceeded any calculated value. This discrepancy could result from limitations of the point dipole approximation in dealing with the distribution of spin density over the sulfur atoms of the cluster and the cysteine ligands, or from differences between the structure in solution and the crystallographic structure. The approach demonstrated here provides a paradigm for a wide range of studies in which hydrogen-bonding interactions with metallic centers has a crucial role in understanding of function. KeywordsRieske iron-sulfur protein; two-dimensional (2D); electron spin echo envelope modulation (ESEEM); hyperfine sublevel correlation (HYSCORE); electron-nuclear double resonance (ENDOR); protons; iron-sulfur cluster

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“…(12) His87 is ligated to the outermost Fe of the [2Fe-2S] center, where, upon reduction, the additional electron is predominantly localized. (13) In addition, pulsed EPR studies indicated that His87 is protonated in the reduced state. (13) At the appropriate pH, protonation of His upon reduction is observed in redox studies on Rieske type [2Fe-2S] centers that involve His coordination.…”

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“…(13) In addition, pulsed EPR studies indicated that His87 is protonated in the reduced state. (13) At the appropriate pH, protonation of His upon reduction is observed in redox studies on Rieske type [2Fe-2S] centers that involve His coordination. 14,15 …”

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Engineering the Redox Potential over a Wide Range within a New Class of FeS Proteins

et al. 2010

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MitoNEET is a newly discovered mitochondrial protein and a target of the TZD class of antidiabetes drugs. MitoNEET is homodimeric with each protomer binding a [2Fe-2S] center through a rare 3-Cys and 1-His coordination geometry. Both the fold and the coordination of the [2Fe-2S] centers suggest that it could have novel properties compared to other known [2Fe-2S] proteins. We tested the robustness of mitoNEET to mutation and the range over which the redox potential (EM) could be tuned. We found that the protein could tolerate an array of mutations that modified the EM of the [2Fe-2S] center over a range of ∼700 mV, which is the largest EM range engineered in an FeS protein and, importantly, spans the cellular redox range (+200 to −300 mV). These properties make mitoNEET potentially useful for both physiological studies and industrial applications as a stable, water-soluble, redox agent.

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¹⁵N HYSCORE Characterization of the Fully Deprotonated, Reduced Form of the Archaeal Rieske [2Fe−2S] Center

Cited by 14 publications

References 24 publications

Identification of Hydrogen Bonds to the Rieske Cluster through the Weakly Coupled Nitrogens Detected by Electron Spin Echo Envelope Modulation Spectroscopy

Identification of Hydrogen Bonds to the Rieske Cluster through the Weakly Coupled Nitrogens Detected by Electron Spin Echo Envelope Modulation Spectroscopy

Proton Environment of Reduced Rieske Iron−Sulfur Cluster Probed by Two-Dimensional ESEEM Spectroscopy

Engineering the Redox Potential over a Wide Range within a New Class of FeS Proteins

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15N HYSCORE Characterization of the Fully Deprotonated, Reduced Form of the Archaeal Rieske [2Fe−2S] Center

Cited by 14 publications

References 24 publications

Identification of Hydrogen Bonds to the Rieske Cluster through the Weakly Coupled Nitrogens Detected by Electron Spin Echo Envelope Modulation Spectroscopy

Identification of Hydrogen Bonds to the Rieske Cluster through the Weakly Coupled Nitrogens Detected by Electron Spin Echo Envelope Modulation Spectroscopy

Proton Environment of Reduced Rieske Iron−Sulfur Cluster Probed by Two-Dimensional ESEEM Spectroscopy

Engineering the Redox Potential over a Wide Range within a New Class of FeS Proteins

Contact Info

Product

Resources

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¹⁵N HYSCORE Characterization of the Fully Deprotonated, Reduced Form of the Archaeal Rieske [2Fe−2S] Center