Mössbauer Study of Cys56Ser Mutant 2Fe Ferredoxin from Clostridium Pasteurianum:  Evidence for Double Exchange in an [Fe2S2]+ Cluster

Achim, Catalina; Golinelli, Marie-Pierre; Bominaar, Emile L.; Meyer, Jacques; Münck, Eckard

doi:10.1021/ja9617698

Cited by 79 publications

(85 citation statements)

References 10 publications

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“…It should be noted that this shortening of the Fe-Fe distance is not a universal consequence of the substitution of Ser for Cys, however, as indicated by the slight increase in this distance in the Ser-49 variant of the Anabaena ferredoxin (34) and the absence of any significant change in the series of model compounds prepared by Coucouvanis and co-workers (41). It is feasible that this slight decrease in the Fe-Fe distance may favor the occurrence of the delocalized mixed valence state, especially because it is consistent with the prediction that transition from the localized to the delocalized valence state is determined by subtle structural modifications (15). Another potentially relevant feature occurs in both the WT and serine-ligated structures, namely, the unique distortion of the Cys-55 S␥-Fe2-S␥-Cys-59 moiety.…”

Section: Discussionsupporting

confidence: 71%

“…The high resolution structures of the C55S and C59S variants of A. aeolicus Fd4 may help illuminate a puzzling property of the counterpart C56S and C60S variants of the homologous protein from C. pasteurianum. In the one-electron reduced [2Fe-2S] ϩ level, these mutated proteins, but not the WT, assume a delocalized mixed valence state resulting in a ground spin state S ϭ 9/2, whereas in all other known cases, [2Fe-2S] ϩ clusters display localized mixed valence states with an S ϭ 1/2 ground spin state (14,15). Although the structures reported here are those of the [2Fe-2S] 2ϩ redox level, they may nevertheless be used, with due caution, in the present discussion.…”

Section: Discussionmentioning

confidence: 99%

“…In their reduced ϩ level, these serine-ligated active sites were found to assume a delocalized mixed valence state having a ground spin state of 9/2 (14,15). This unprecedented occurrence in binuclear iron-sulfur clusters has stimulated experimental and theoretical work (16,17).…”

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High Resolution Crystal Structures of the Wild Type and Cys-55 → Ser and Cys-59 → Ser Variants of the Thioredoxin-like [2Fe-2S] Ferredoxin from Aquifex aeolicus

Yeh

Ambroggio

Andrade

et al. 2002

Journal of Biological Chemistry

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The low potential iron-sulfur (Fe-S) electron carriers known as ferredoxins (Fds) 1 are found in three distinct classes, the (7), and Aquifex aeolicus (8). The high level of similarity of these proteins allows for easy transfer of structural information among them. For instance, many properties of molecular variants of the C. pasteurianum [2Fe-2S] Fd (6, 9, 10) could be rationalized from the crystal structure of A. aeolicus Fd4 (11). This structure established the unexpected thioredoxin-like fold of these Fds and confirmed that they are distinct from the other two ferredoxin classes (1). The 2.3 Å resolution of the Fd4 structure, however, was not among the highest currently reported (about 1 Å) for metalloenzymes. Indeed, such high resolution structures are of utmost interest because they bring forth precise geometries of metal sites (4) and may allow description of redox transitions (5). Additional efforts have therefore been made, both on wild type (WT) thioredoxin-like Fds and on several of the molecular variants that were produced over the years (6,10,12), with the aim of improving the crystallographic data.In some modified forms of C. pasteurianum Fd, cysteine ligands of the Fe-S cluster were replaced by serine (9, 13). In their reduced ϩ level, these serine-ligated active sites were found to assume a delocalized mixed valence state having a ground spin state of 9/2 (14, 15). This unprecedented occurrence in binuclear iron-sulfur clusters has stimulated experimental and theoretical work (16,17). The development of these investigations has been hampered, however, by the absence of structural data on serine-ligated [2Fe-2S] active sites and their environment. Because only the Fd4 from A. aeolicus has been crystallized, we have repeated amino acid substitutions in that protein previously performed on C. pasteurianum Fd and produced the C55S and C59S variants that contain serine-ligated [2Fe-2S] clusters. We report here the high resolution structures for both of these variants as well as WT protein which provide accurate metric details for serine-ligated Fe-S clusters in proteins. EXPERIMENTAL PROCEDURESProtein Samples-Fd4 from A. aeolicus was purified as described by Chatelet et al. (8). The C55S and C59S variants were prepared by site-directed mutagenesis as described for the C56S and C60S counterparts from C. pasteurianum (13). The mutagenic oligonucleotides were

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Section: Discussionsupporting

confidence: 71%

Section: Discussionmentioning

confidence: 99%

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High Resolution Crystal Structures of the Wild Type and Cys-55 → Ser and Cys-59 → Ser Variants of the Thioredoxin-like [2Fe-2S] Ferredoxin from Aquifex aeolicus

Yeh

Ambroggio

Andrade

et al. 2002

Journal of Biological Chemistry

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“…Such a localization-to-delocalization transition of the merging type has not been observed in physiological protein-bound [2Fe-2S] clusters, but has been observed only in a few synthetic model compounds with mixed-valence [2Fe-2S] cores [40]. A particular temperature-dependent valence delocalization has also been observed in a cysteine to serine mutated [2Fe-2S] ferredoxin from C. pasteurianum [37,38]. This mutant is composed of a mixture of two species in two spin states, a valence-delocalized high-spin form with S = 9/2 (Fd 9/2 ) and a valence-localized form with S = 1/2 (Fd 1/2 ), with the Fd 1/2 fraction performing a temperature-dependent localization-to-delocalization transition without changing the spin state.…”

Section: Reduced Fl Constructmentioning

confidence: 97%

Human anamorsin binds [2Fe–2S] clusters with unique electronic properties

et al. 2013

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The eukaryotic anamorsin protein family, which has recently been proposed to be part of an electron transfer chain functioning in the early steps of cytosolic iron-sulfur (Fe/S) protein biogenesis, is characterized by a largely unstructured domain (CIAPIN1) containing two conserved cysteine-rich motifs (CX 8 CX 2 CXC and CX 2 CX 7 CX 2 C) whose Fe/S binding properties and electronic structures are not well defined. Here, we found that (1) each motif in human anamorsin is able to bind independently a [2Fe-2S] cluster through its four cysteine residues, the binding of one cluster mutually excluding the binding of the second, (2) the reduced [2Fe-2S] ? clusters exhibit a unique electronic structure with considerable anisotropy in their coordination environment, different from that observed in reduced, plant-type and vertebratetype [2Fe-2S] ferredoxin centers, (3) the reduced cluster bound to the CX 2 CX 7 CX 2 C motif reveals an unprecedented valence localization-to-delocalization transition as a function of temperature, and (4) only the [2Fe-2S] cluster bound to the CX 8 CX 2 CXC motif is involved in the electron transfer with its physiological protein partner Ndor1. The unique electronic properties of both [2Fe-2S] centers can be interpreted by considering that both cysteine-rich motifs are located in a highly unstructured and flexible protein region, whose local conformational heterogeneity can induce anisotropy in metal coordination. This study contributes to the understanding of the functional role of the CIAPIN1 domain in the anamorsin family, suggesting that only the [2Fe-2S] cluster bound to the CX 8 CX 2 CXC motif is indispensable in the electron transfer chain assembling cytosolic Fe/S proteins.

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“…a non-Cys ligand) and may favor one or the other spin arrangement. Cases for this are documented, with one of the simplest and most impressive examples being the 2Fe ferredoxin from a mutant of Clostridium pasteurianum in which one serine replaces one of the cysteine ligands of the native structure (30).…”

Section: Reflections: Bioinorganic Chemistry: a New Field?mentioning

confidence: 99%

Bioinorganic Chemistry: A New Field or Discipline? Words, Meanings, and Reality

Beinert

2002

Journal of Biological Chemistry

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Mössbauer Study of Cys56Ser Mutant 2Fe Ferredoxin from Clostridium Pasteurianum: Evidence for Double Exchange in an [Fe₂S₂]⁺ Cluster

Cited by 79 publications

References 10 publications

High Resolution Crystal Structures of the Wild Type and Cys-55 → Ser and Cys-59 → Ser Variants of the Thioredoxin-like [2Fe-2S] Ferredoxin from Aquifex aeolicus

High Resolution Crystal Structures of the Wild Type and Cys-55 → Ser and Cys-59 → Ser Variants of the Thioredoxin-like [2Fe-2S] Ferredoxin from Aquifex aeolicus

Human anamorsin binds [2Fe–2S] clusters with unique electronic properties

Bioinorganic Chemistry: A New Field or Discipline? Words, Meanings, and Reality

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