Spectroelectrochemical studies of the corrinoid/iron-sulfur protein involved in acetyl coenzyme A synthesis by Clostridium thermoaceticum

Harder, Scott R.; Lu, Wei; Feinberg, Benjamin A.; Ragsdale, Stephen W.

doi:10.1021/bi00449a019

Cited by 98 publications

(123 citation statements)

References 33 publications

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“…60 This difference perhaps reflects the necessity of the [Fe 4 S 4 ] cluster of CFeSP to possess a somewhat unique electronic structure as judged on the basis of the unusually low midpoint potential of -523 mV versus SHE. 13 While both the Abs and CD spectroscopic data of the Co 2+ CFeSP presented above contain significant contributions from the diamagnetic [Fe 4 S 4 ] 2+ cluster, the corresponding 4.5 K 7 T MCD spectrum should be dominated entirely by the corrinoid features due to the dramatic enhancement of MCD C-terms arising from paramagnetic species at low temperatures. Indeed, all features in the Co 2+ CFeSP MCD spectrum ( Figure 2) were found to decrease in intensity with increasing temperature as predicted for an S = 1 / 2 species.…”

Section: Results and Analysis Spectroscopic Studies (I) Abs CD Andmentioning

confidence: 90%

“…The fact that the positions of all four features are identical (within experimental error) in the two difference spectra indicates that the electronic properties of the [Fe 4 S 4 ] 2+ cluster do not depend on the Co oxidation state, consistent with previous potentiometric studies. 13 As both the methylated Factor III m and the oxidized [Fe 4 S 4 ] 2+ cluster are diamagnetic, the MCD spectral intensity of Me-Co 3+ CFeSP should be temperature-independent. However, the corresponding MCD spectrum obtained at 7 T actually exhibited temperature-dependent features attributed to a minor fraction of reduced Co 2+ CFeSP (cf.…”

Section: Abs CD and Mcd Spectra Of Me-co 3+ Cfespmentioning

confidence: 99%

“…Likewise, the addition of mersalyl acid, which disrupts the [Fe 4 S 4 ] cluster without perturbing the EPR spectrum of the CFeSP-bound Co 2+ corrinoid cofactor, has negligible effects on the midpoint potential of the Co 2+/1+ couple, demonstrating that the two metal cofactors are electronically uncoupled. 13 While the functional roles of both metal cofactors in CFeSP are well understood, fundamental questions concerning the exact nature of the coordination environment of the corrinoid remain unanswered. Results from previous X-ray absorption fine structure (EXAFS) studies of both Me-Co 3+ CFeSP and Co 2+ CFeSP suggested that, in each case, the enzyme-bound corrinoid lacks a lower axial ligand, thus adopting an unprecedented five-coordinate and four-coordinate Co-coordination environment, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Spectroscopic Studies of the Corrinoid/Iron−Sulfur Protein from Moorella thermoacetica

et al. 2006

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Methyl transfer reactions are important in a number of biochemical pathways. An important class of methyltransferases uses the cobalt cofactor cobalamin, which receives a methyl group from an appropriate methyl donor protein to form an intermediate organometallic methyl-Co bond that subsequently is cleaved by a methyl acceptor. Control of the axial ligation state of cobalamin influences both the mode (i.e., homolytic vs heterolytic) and the rate of Co-C bond cleavage. Here we have studied the axial ligation of a corrinoid iron-sulfur protein (CFeSP) that plays a key role in energy generation and cell carbon synthesis by anaerobic microbes, such as methanogenic archaea and acetogenic bacteria. This protein accepts a methyl group from methyltetrahydrofolate forming Me-Co 3+ CFeSP that then donates a methyl cation (Me) from Me-Co 3+ CFeSP to a nickel site on acetyl-CoA synthase. To unambiguously establish the binding scheme of the corrinoid cofactor in the CFeSP, we have combined resonance Raman, magnetic circular dichroism, and EPR spectroscopic methods with computational chemistry. Our results clearly demonstrate that the MeCo 3+ and Co 2+ states of the CFeSP have an axial water ligand like the free MeCbi + and Co 2+ Cbi + cofactors; however, the Co-OH 2 bond length is lengthened by about 0.2 Å for the protein-bound cofactor. Elongation of the Co-OH 2 bond of the CFeSP-bound cofactor is proposed to make the cobalt center more "Co 1+ -like", a requirement to facilitate heterolytic Co-C bond cleavage.

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Section: Results and Analysis Spectroscopic Studies (I) Abs CD Andmentioning

confidence: 90%

Section: Abs CD and Mcd Spectra Of Me-co 3+ Cfespmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spectroscopic Studies of the Corrinoid/Iron−Sulfur Protein from Moorella thermoacetica

et al. 2006

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“…Neither dimethylbenzimidazol nor a protein side chain is bound to the cobalt ion in the structure. Based on a comparison of redox potentials between proteins with (5-methoxybenzimidazolyl)cobamide, free corrinoids, and CoFeSP Mt from M. thermoacetica, it was suggested that the uncoordinated cob(I)amide is stabilized by approximately ϩ100 mV compared with the ''base-on'' or ''His-on'' states (15). This ''base-off͞His-off'' conformation increases the population of the cob(I)amide state and, in cases of unwanted oxidations of the cofactor, the more facile reduction of the cofactor.…”

Section: Resultsmentioning

confidence: 99%

Structural insights into methyltransfer reactions of a corrinoid iron–sulfur protein involved in acetyl-CoA synthesis

Svetlitchnaia¹,

Svetlitchnyi²,

Meyer

et al. 2006

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

106

146

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acety-CoA pathway ͉ Carboxydothermus hydrogenoformans ͉ methyltransferase ͉ cobalt B 12-dependent enzymes are widespread in nature and catalyze distinct reactions. They can be grouped in three major classes: the isomerases, reductive dehalogenases, and methyltransferases (MeTrs; ref. 1). The cobalamin-dependent MeTrs play important roles in the amino acid biosynthesis in many organisms, ranging from bacteria to humans, as well as in the one-carbon metabolism of bacteria and archaea. MeTrs typically catalyze the transfer of methyl groups between organic and inorganic donors and acceptors like S-adenosylmethionine, methyltetrahydrofolate, and cobalamins. A unique methyltransfer reaction is found within the acetyl-CoA (Ljungdahl-Wood) pathway of autotrophic carbon assimilation, which operates in the anaerobic acetogenic, sulfidogenic, methanogenic, and hydrogenogenic bacteria and archaea. In the final step of the pathway, acetyl-CoA is synthesized from a methyl cation, carbon monoxide (CO), and CoA, a reaction catalyzed by the Ni-and Fe-containing enzyme acetyl-CoA synthase (ACS; for a review, see ref.2). Key to this reaction (Eq. 1) is the action of the Coand Fe-containing corrinoid iron-sulfur protein (CoFeSP) that donates the methyl group from methyl-cob(III)amide to one of the two Ni ions in the active site cluster A of ACS (3). This is the only methyltransfer reaction known with metals as donors and acceptors of the methyl group: CH 3 OCoFeSP ϩ CO ϩ CoA 3 CH 3 (CO)CoA ϩ CoFeSP. [1]CoFeSP has been isolated and characterized from the acetogenic bacterium Moorella thermoacetica (4), the methanogenic archaeon Methanosarcina thermophila (5), and the hydrogenogenic bacterium Carboxydothermus hydrogenoformans (6).C. hydrogenoformans can use CO as a sole source of energy and carbon under anaerobic chemolithoautotrophic conditions. Protons serve as terminal electron acceptor (7), and the methyl branch of the acetyl-CoA pathway is used for the assimilation of carbon (6). The oxidation of CO in this bacterium is catalyzed by two monofunctional NiFe-containing CODHs (CODHI Ch and CODHII Ch ) that harbor the [Ni-4Fe-5S] active site cluster C (7). A monomeric ACS Ch , a 1:1 molar complex of ACS Ch and CODHIII Ch , and CoFeSP Ch are expressed in functional form during the growth of C. hydrogenoformans using CO as the only substrate (6). The CoFeSP Ch from C. hydrogenoformans is a heterodimeric protein composed of a large subunit (48.4 kDa, CfsA) and a small subunit (33.9 kDa, CfsB) and harbors one molecule of the cobalt-containing corrinoid cofactor and a single The CoFeSPs from acetogens and methanogens are heterodimeric proteins sharing sequence identities of 35-53% with CoFeSP Ch from C. hydrogenoformans. CoFeSP Mt from M. thermoacetica was shown to contain two cofactors, 5-methoxybenzimidazolylcobamide (a variant of B12) and a [4Fe-4S] 2ϩ/1ϩ cluster, which gave the protein its name. For the cobamide cofactor, it was shown that neither the 5-methoxybenzimidazolyl group nor a nitrogen atom from a protein side chain is coor...

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“…The absence of protein ligands is the probable reason why the redox potential of the Co 2þ ∕Co 1þ couple of CoFeSP is about 50-100 mV more positive than in other corrinoid containing methyltransferases (25,33), rendering it reducible by electrons generated from the oxidation of CO by carbon monoxide dehydrogenases (26). The necessity for an ATP-dependent reductive activator has therefore not been anticipated.…”

Section: Discussionmentioning

confidence: 99%

Redox-dependent complex formation by an ATP-dependent activator of the corrinoid/iron-sulfur protein

Hennig

Jeoung

Goetzl

et al. 2012

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

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Movement, cell division, protein biosynthesis, electron transfer against an electrochemical gradient, and many more processes depend on energy conversions coupled to the hydrolysis of ATP. The reduction of metal sites with low reduction potentials (E 0 0 < −500 mV) is possible by connecting an energetical uphill electron transfer with the hydrolysis of ATP. The corrinoid-iron/ sulfur protein (CoFeSP) operates within the reductive acetyl-CoA pathway by transferring a methyl group from methyltetrahydrofolate bound to a methyltransferase to the [Ni-Ni-Fe 4 S 4 ] cluster of acetyl-CoA synthase. Methylation of CoFeSP only occurs in the lowpotential Co(I) state, which can be sporadically oxidized to the inactive Co(II) state, making its reductive reactivation necessary. Here we show that an open-reading frame proximal to the structural genes of CoFeSP encodes an ATP-dependent reductive activator of CoFeSP. Our biochemical and structural analysis uncovers a unique type of reductive activator distinct from the electron-transferring ATPases found to reduce the MoFe-nitrogenase and 2-hydroxyacyl-CoA dehydratases. The CoFeSP activator contains an ASKHA domain (acetate and sugar kinases, Hsp70, and actin) harboring the ATP-binding site, which is also present in the activator of 2-hydroxyacyl-CoA dehydratases and a ferredoxin-like [2Fe-2S] cluster domain acting as electron donor. Complex formation between CoFeSP and its activator depends on the oxidation state of CoFeSP, which provides evidence for a unique strategy to achieve unidirectional electron transfer between two redox proteins.

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Spectroelectrochemical studies of the corrinoid/iron-sulfur protein involved in acetyl coenzyme A synthesis by Clostridium thermoaceticum

Cited by 98 publications

References 33 publications

Spectroscopic Studies of the Corrinoid/Iron−Sulfur Protein from Moorella thermoacetica

Spectroscopic Studies of the Corrinoid/Iron−Sulfur Protein from Moorella thermoacetica

Structural insights into methyltransfer reactions of a corrinoid iron–sulfur protein involved in acetyl-CoA synthesis

Redox-dependent complex formation by an ATP-dependent activator of the corrinoid/iron-sulfur protein

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