Calculation of the Redox Potentials of Iron-Sulfur Proteins: The 2-/3- Couple of [Fe4S4Cys4] Clusters in Peptococcus aerogenes Ferredoxin, Azotobacter vinelandii Ferredoxin I, and Chromatium vinosum High-Potential Iron Protein

Jensen, Greg; Warshel, Arieh; Stephens, Philip J.

doi:10.1021/bi00202a010

Cited by 115 publications

(126 citation statements)

References 57 publications

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“…Even lower values were predicted for the non-physiological 2ϩ/ϩ transition of [4Fe-4S] clusters in high potential ferredoxins and in E. coli endonuclease III (42). The structures of oxidized Peptostreptococcus asaccharolyticus ferredoxin and of A. vinelandii ferredoxin I have been used to calculate the reduction potential of the [4Fe-4S] clusters in these proteins (43). The 250 mV less negative potential in the former was explained by the occurrence of additional Langevin dipoles in the vicinity of cluster I in P. asaccharolyticus ferredoxin.…”

Section: Factors Contributing To the Reduction Potential Of Cluster Imentioning

confidence: 99%

The Two [4Fe-4S] Clusters in Chromatium vinosumFerredoxin Have Largely Different Reduction Potentials

Kyritsis¹,

Hatzfeld²,

Link³

et al. 1998

Journal of Biological Chemistry

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Section: Factors Contributing To the Reduction Potential Of Cluster Imentioning

confidence: 99%

The Two [4Fe-4S] Clusters in Chromatium vinosumFerredoxin Have Largely Different Reduction Potentials

Kyritsis¹,

Hatzfeld²,

Link³

et al. 1998

Journal of Biological Chemistry

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“…These structural features, confirmed by resonance Raman (Backes et al, 1991) and electron spin echo studies (Orme-Johnson et al, 1983), were first proposed as determinants of the accessible oxidation states of [4Fe-4S] cluster in HiPIPs versus ferredoxins more than 20 years ago (Carter et al, 1972). This view has recently been refined by proteindipole Langevin dipole calculations, a study in which the role of the polarity of the amide groups surrounding the cluster in determining the reduction potential of the latter was stressed (Jensen et al, 1994). Although HiPIPs share considerable similarity in their tertiary structures, they show surprising variability in their amino acid sequences and overall charges.…”

mentioning

confidence: 91%

The role of a conserved tyrosine residue in high‐potential iron sulfur proteins

et al. 1995

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Conserved tyrosine-12 of Ectofhiorhodospira hdophikz high-potential iron sulphur protein (HiPIP) iso-I was substituted with phenylalanine (Y12F), histidine (Y 12H), tryptophan (Y 12W), isoleucine (Y 12I), and alanine (Y 12A). Variants Y 12A and Y12I were expressed to reasonable levels in cells grown at lower temperatures, but decomposed during purification. Variants Y 12F, Y12H, and Y 12W were substantially destabilized with respect to the recombinant wild-type HiPIP (rcWT) as determined by differential scanning calorimetry over a pH range of 7.0-1 1 .O. Characterization of the Y 12F variant by NMR indicates that the principal structural differences between this variant and the rcWT HiPIP result from the loss of the two hydrogen bonds of the Tyr-12 hydroxyl group with Asn-14 0 6 1 and Lys-59 NH, respectively. The effect of the loss of the latter interaction is propagated through the Lys-591 Val-58 peptide bond, thereby perturbing Gly-46. The AAG;j.. of Y12F of 2.3 kcal/mol with respect to rcWT HiPlP (25 "C, pH 7.0) is entirely consistent with the contribution of these two hydrogen bonds to the stability of the latter. CD measurements show that Tyr-12 influences several electronic transitions within the cluster. The midpoint reduction potentials of variants Y 12F, Y12H, and Y12W were 17, 19, and 22 mV (20 mM MOPS, 0.2 M sodium chloride, pH 6.98, 25 "C), respectively, higher than that of rcWT HiPIP. The current results indicate that, although conserved Tyr-12 modulates the properties of the cluster, its principle function is to stabilize the HiPIP through hydrogen bonds involving its hydroxyl group and electrostatic interactions involving its aromatic ring.

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“…In the light of the present study, this model appears to be overly simplistic because the FA 2 (V49I/K52T/R53Q) mutations also remove these positive charges close to F A but do not lead to preferential F B reduction. In line with this, it has been recently stressed that redox potentials of Fe-S clusters are determined by many parameters, among which the protein dipoles surrounding the clusters and the solvent accessibility are important (53)(54)(55). These parameters are beyond evaluation with the present structural knowledge of PSI.…”

Section: Discussionmentioning

confidence: 98%

Site-directed Mutagenesis of the PsaC Subunit of Photosystem I

Fischer¹,

Sétif²,

Rochaix³

1999

Journal of Biological Chemistry

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The two [4Fe-4S] clusters F A and F B are the terminal electron acceptors of photosystem I (PSI) that are bound by the stromal subunit PsaC. Soluble ferredoxin (Fd) binds to PSI via electrostatic interactions and is reduced by the outermost iron-sulfur cluster of PsaC. We have generated six site-directed mutants of the green alga Chlamydomonas reinhardtii in which residues located close to the iron-sulfur clusters of PsaC are changed. The acidic residues Asp 9 and Glu 46 , which are located one residue upstream of the first cysteine liganding cluster F B and F A , respectively, were changed to a neutral or a basic amino acid. Although Fd reduction is not affected by the E46Q and E46K mutations, a slight increase of Fd affinity (from 1.3-to 2-fold) was observed by flash absorption spectroscopy for the D9N and D9K mutant PSI complexes. In the FA 2 triple mutant (V49I/K52T/R53Q), modification of residues located next to the F A cluster leads to partial destabilization of the PSI complex. The electron paramagnetic resonance properties of cluster F A are affected, and a 3-fold decrease of Fd affinity is observed. The introduction of positively charged residues close to the F B cluster in the FB 1 triple mutant (I12V/T15K/Q16R) results in a 60-fold increase of Fd affinity as measured by flash absorption spectroscopy and a larger amount of PsaC-Fd cross-linking product. The first-order kinetics are similar to wild type kinetics (two phases with t1 ⁄2 of <1 and Ϸ4.5 s) for all mutants except FB 1 , where Fd reduction is almost monophasic with t1 ⁄2 < 1 s. These data indicate that F B is the cluster interacting with Fd and therefore the outermost iron-sulfur cluster of PSI.

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Calculation of the Redox Potentials of Iron-Sulfur Proteins: The 2-/3- Couple of [Fe4S4Cys4] Clusters in Peptococcus aerogenes Ferredoxin, Azotobacter vinelandii Ferredoxin I, and Chromatium vinosum High-Potential Iron Protein

Cited by 115 publications

References 57 publications

The Two [4Fe-4S] Clusters in Chromatium vinosumFerredoxin Have Largely Different Reduction Potentials

The Two [4Fe-4S] Clusters in Chromatium vinosumFerredoxin Have Largely Different Reduction Potentials

The role of a conserved tyrosine residue in high‐potential iron sulfur proteins

Site-directed Mutagenesis of the PsaC Subunit of Photosystem I

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