Mutation of the surface valine residues 8 and 44 in the rubredoxin from Clostridium pasteurianum : solvent access versus structural changes as determinants of reversible potential

Xiao, Zhiguang; Maher, M.J.; Cross, Mervyn J.; Bond, Charles S.; Guss, J.M.; Wedd, A. G.

doi:10.1007/pl00010656

Cited by 36 publications

(59 citation statements)

References 32 publications

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“…Detailed comparison of available x-ray crystal structures of CpRd variants has revealed that slight changes in the structure surrounding the iron-sulfur cluster are responsible for the range of observed reduction potentials (15,16,28). In our study, 15 N hyperfine shifts were used to detect subtle changes in H N ⅐⅐⅐⅐⅐S ␥ bond lengths in CpRd variants.…”

Section: Discussionmentioning

confidence: 89%

“…The covalent character of the iron-sulfur bonds in CpRd and PfRd has been determined quantitatively by K-edge x-ray absorption spectroscopy; however, these studies revealed no direct correlation between iron-sulfur covalency and the reduction potential (14). A further detailed comparison of the crystal structures ascribed the reduction potential difference to different orientations of the peptide dipole at residue 44, along with a change in the distance between the Xaa44 N and Cys-42 S ␥ (15,16).…”

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confidence: 99%

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Changes in hydrogen-bond strengths explain reduction potentials in 10 rubredoxin variants

Lin¹,

Gebel²,

Machonkin³

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

113

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The rubredoxin from Clostridium pasteurianum (CpRd) provides an excellent system for investigating how the protein sequence modulates the reduction potential of the active site in an iron-sulfur protein. 15 N NMR spectroscopy has allowed us to determine with unprecedented accuracy the strengths of all six key hydrogen bonds between protein backbone amides and the sulfur atoms of the four cysteine residues that ligate the iron in the oxidized (Fe III ) and reduced (Fe II ) forms of wild-type CpRd and nine mutants (V44G, V44A, V44I, V44L, V8G, V8A, V8I, V8L, and V8G͞V44G). The length (or strength) of each hydrogen bond was inferred from the magnitude of electron spin delocalized across the hydrogen bond from the iron atom onto the nitrogen. The aggregate lengths of these six hydrogen bonds are shorter in both oxidation states in variants with higher reduction potential than in those with lower reduction potential. Differences in aggregate hydrogen bonding upon reduction correlate linearly with the published reduction potentials for the 10 CpRd variants, which span 126 mV. Sequence effects on the reduction potential can be explained fully by their influence on hydrogen-bond strengths.iron-sulfur protein ͉ reduction potential tuning ͉ 15 N NMR ͉ paramagnetic NMR

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Section: Discussionmentioning

confidence: 89%

mentioning

confidence: 99%

Changes in hydrogen-bond strengths explain reduction potentials in 10 rubredoxin variants

Lin¹,

Gebel²,

Machonkin³

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

113

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“…These hydrogen bonds are purported to serve a dual purpose: they tune the cofactor E m as well as define ET pathways [65][66][67]. Markley and coworkers reported a 15 N NMR study of mutants of Val44 in Clostridium pasteurianum rubredoxin in which the hydrogen bond from the backbone amide at position 44 to the iron-ligating Cys42 varies systematically [68,69]. In these variants, no significant changes are noticed in the lengths of other hydrogen bonds.…”

Section: Rubredoxinsmentioning

confidence: 99%

Biological Outer-Sphere Coordination

Lancaster

2011

Molecular Electronic Structures of Transition Metal Complexes I

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The concept of outer-sphere coordination (OSC) is surveyed in the context of bioinorganic chemistry. A distinction is made between electronic and structural OSC, both arising from the interaction of the protein matrix with inner sphere ligands. Electronic OSC entails the electronic interaction between the polypeptide and inner-sphere ligands. These effects principally arise from hydrogenbonding interactions, though through-space dipolar interactions are also encountered. Structural OSC comprises primarily steric effects that do not necessarily impact ligand electronics but rather influence inner sphere topology. Additionally, the protein matrix can be envisioned as a local "solvent" whose bulk dielectric and point charges influence the metal center. Recurring themes are highlighted where OSC regulates the properties of various metalloproteins distinguished by cofactors and/or function. Finally, cases are presented where OSC has guided molecular design.

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“…Factors that have been proposed as being important include (a) solvent exposure of the cluster, (b) specific hydrogen bonding networks especially NH-S bonds, (c) the proximity and orientation of protein backbone and side chain dipoles, and/or (d) the proximity of charged residues to the cluster (7,(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35). This study concerns protein control of the reduction potential of a [4Fe-4S] 2ϩ/ϩ cluster that is ligated via a typical CXXCXXC motif with one remote Cys ligand.…”

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confidence: 99%

Azotobacter vinelandii Ferredoxin I

Chen¹,

Jung²,

Bonagura³

et al. 2002

Journal of Biological Chemistry

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The reduction potential (E 0 ) of the [4Fe-4S]2؉/؉ cluster of Azotobacter vinelandii ferredoxin I (AvFdI) and related ferredoxins is ϳ200 mV more negative than the corresponding clusters of Peptostreptococcus asaccharolyticus ferredoxin and related ferredoxins. Previous studies have shown that these differences in E 0 do not result from the presence or absence of negatively charged surface residues or in differences in the types of hydrophobic residues found close to the Most iron-sulfur ([Fe-S]) proteins are intimately involved in essential electron transfer reactions, including membranebound electron transport systems; their functions, however, are not restricted to electron transfer and include direct catalysis of hydration/dehydration reactions, O 2 and iron sensing, regulation of gene expression, iron storage, metal cluster assembly, and the generation and stabilization of radical intermediates (for reviews, see Refs. 1-6). To meet these diverse functions, individual proteins have increased the variety of [Fe-S] cluster structures by adding or subtracting iron and sulfide atoms to vary the cluster type, or by introducing noncysteine ligands. Even after adopting a specific cluster type (e.g. [4Fe-4S] clusters with four cysteine ligands), proteins can control reactivity further by stabilizing a particular redox couple (e.g. 3ϩ/2ϩ, 2ϩ/ϩ, or ϩ/0) or by modulation of the reduction potential (E 0 Ј) of a particular redox couple (7-19). Thus, high potential iron proteins have 3ϩ/2ϩ E 0 Ј ranging from 90 to 450 mV (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)20), while ferredoxins that contain structurally indistinguishable 2ϩ/ϩ clusters have E 0 Ј ranging from Ϫ280 to Ϫ715 mV in different native proteins (10, 21).Both experimental and theoretical research has been directed toward understanding how the polypeptide surrounding the cluster controls the reduction potential. Factors that have been proposed as being important include (a) solvent exposure of the cluster, (b) specific hydrogen bonding networks especially NH-S bonds, (c) the proximity and orientation of protein backbone and side chain dipoles, and/or (d) the proximity of charged residues to the cluster (7,(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35). This study concerns protein control of the reduction potential of a 2ϩ/ϩ cluster that is ligated via a typical CXXCXXC motif with one remote Cys ligand.Previous studies in this area have focused on comparing the environments of the clusters in structurally characterized proteins. 2ϩ/ϩ cluster of Azotobacter vinelandii ferredoxin I (AvFdI) 1 has a low E 0 Ј of about Ϫ620 mV (pH 7.0) (36), whereas the analogous clusters in Peptostreptococcus asaccharolyticus ferredoxin (PaFd) and Clostridium acidiurici ferredoxin have E 0 Ј of about Ϫ430 mV (not pH-dependent) (37). Comparison of the structures of these proteins showed that the peptide folding around the analogous clusters is highly conserved with respect to the location of the four Cys ligands, the Cys dihedral angles, and the eight amide groups hydr...

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Mutation of the surface valine residues 8 and 44 in the rubredoxin from Clostridium pasteurianum : solvent access versus structural changes as determinants of reversible potential

Cited by 36 publications

References 32 publications

Changes in hydrogen-bond strengths explain reduction potentials in 10 rubredoxin variants

Changes in hydrogen-bond strengths explain reduction potentials in 10 rubredoxin variants

Biological Outer-Sphere Coordination

Azotobacter vinelandii Ferredoxin I

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