Structure and electronic properties of an asymmetric thiolate-bridged binuclear complex: a model for the active site of acetyl CoA synthase

Wang, Qiang; Blake, Alexander J.; Davies, E. Stephen; McInnes, Eric J. L.; Wilson, Claire; Schröder, Martin

doi:10.1039/b310183e

Cited by 43 publications

(72 citation statements)

References 21 publications

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“…The redox behaviors of the models of the Ni d sites reported so far suggest that the Ni d site of the A-cluster is unlikely to participate in any redox process during catalysis and in turn imply that the Ni p site is a candidate for reduction and CO binding during the ACS catalyzed reaction. [19][20][21][22][23][24][25] The Ni C centers of the trinuclear species 6 and 8 are ligated to four metallosulfur ligands and hence resemble the Ni p site to a great extent. Both these models can be chemically reduced with reductants like Na 2 S 2 O 4 and NaBH 4 at low temperature (−40 °C) to afford EPR-active species.…”

Section: Reactivity Of Ni-ni Modelsmentioning

confidence: 99%

“…18 Since the publication of the first structure of ACS/CODH, several low molecular weight models of the ACS site have been synthesized and studied to determine the intrinsic properties of the metal-containing active site(s). [19][20][21][22][23][24][25] In these pursuits, researchers have focused mostly on the bimetallic M p -Ni d site of ACS and ignored the Fe 4 S 4 portion (unlikely site of substrate binding). For example, Rauchfuss and coworkers have synthesized the model complex [{Ni(CO) 2 }{NiS 2 N' 2 }] 2− (structure a, Figure 2) with two terminal CO ligands bound to the bridged Ni center in the 0 oxidation state.…”

Section: Introductionmentioning

confidence: 99%

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Synthetic Analogues of the Active Site of the A-Cluster of Acetyl Coenzyme A Synthase/CO Dehydrogenase: Syntheses, Structures, and Reactions with CO

2006

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Two metallosynthons, namely (Et 4 N) 2 [Ni(NpPepS)] (1) and (Et 4 N) 2 [Ni(PhPepS)] (2) containing carboxamido-N and thiolato-S as donors have been used to model the bimetallic M p -Ni d subsite of the A-cluster of the enzyme ACS/CODH. A series of sulfurbridged Ni/Cu dinuclear and trinuclear complexes (3-10) have been synthesized to explore their redox properties and affinity of the metal centers toward CO. The structures of (Et 4 N) 2 (8), and [Ni(dppe)Ni(PhPepS)]•CH 2 Cl 2 (10•CH 2 Cl 2 ) have been determined by crystallography. The Ni d mimics 1 and 2 resist reduction and exhibit no affinity toward CO. In contrast, the sulfur-bridged Ni center (designated Ni C ) in the trinuclear models 5-8 are amenable to reduction and binds CO in the Ni(I) state. Also, the sulfurbridged Ni C center can be removed from the trimers (5-8) by treatment with 1,10-phenanthroline much like the "labile Ni" from the enzyme. The dinuclear Ni-Ni models 9 and 10 resemble the Ni p -Ni d subsite of the A-cluster more closely and only the modeled Ni p site of the dimers can be reduced. The Ni(I)-Ni(II) species display EPR spectra typical of a Ni(I) center in distorted trigonal bipyramidal and distorted tetrahedral geometries for 9 red and 10 red , respectively. Both species bind CO and the CO-adducts 9 red -CO and 10 red -CO display strong ν co at 2044 and 1997 cm -1 , respectively. The reduction of 10 is reversible. The CO-affinity of 10 in the reduced state and the ν co value of 10 red -CO closely resemble the CO-bound reduced A-cluster (ν co = 1996 cm -1 ).

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Section: Reactivity Of Ni-ni Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Synthetic Analogues of the Active Site of the A-Cluster of Acetyl Coenzyme A Synthase/CO Dehydrogenase: Syntheses, Structures, and Reactions with CO

2006

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“…The order of the addition of the substrates, Me, CO, and CoA, to the active site is also controversial, and several mechanisms have been proposed on the basis of biological and computational studies (12)(13)(14). On the other hand, synthetic studies that probe the reaction mechanisms are limited in number, although various thiolato-bridged dinuclear nickel complexes have been reported as A-cluster models (15)(16)(17)(18)(19)(20)(21)(22)(23).…”

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confidence: 99%

Dinuclear nickel complexes modeling the structure and function of the acetyl CoA synthase active site

Ito

Kotera

Matsumoto

et al. 2009

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

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acetylthioester formation ͉ dinuclear nickel-site model ͉ N2S2 ligand ͉ nickel acyl complex A cetyl-CoA synthase/CO dehydrogenase (ACS/CODH), a bifunctional metalloenzyme found in acetogenic, methanogenic, and sulfate-reducing bacteria, has the important function of fixing CO and CO 2 in the global carbon cycle (1-3). Whereas CODH catalyzes the reversible conversion of CO 2 to CO, ACS assembles acetyl-CoA from CO, CoA, and a methyl moiety that is derived from the methylcobalamin of the corrinoid iron-sulfur protein (CFeSP). Recently, the crystal structures of the ACS/ CODH system from the bacteria Moorella thermoacetica and Carboxydothermus hydrogenoformans have been elucidated (4-6); the ACS active site denoted as the A-cluster contains a [Fe 4 S 4 ] cubane cluster and a Ni d -Ni p dinuclear site as shown in Fig. 1, where the 2 nickels designated as Ni d and Ni p occupy distal and proximal positions, respectively, to the [Fe 4 S 4 ] cluster. The geometry around Ni d is square planar, composed of 2 cysteine sulfurs and 2 carboxyamide nitrogens of the tripeptide Cys-GlyCys from the protein backbone. Ni p carries an unidentified ligand X and 3 bridging cysteine sulfurs, 2 from the aforementioned tripeptide, and 1 from the [Fe 4 S 4 ] cluster.Biological investigations suggest that the oxidized state of the cluster A ox should be formulated as {Ni d 2ϩ -Ni p 2ϩ -[Fe 4 S 4 ] 2ϩ } (7-9). However, the electronic configuration of the active reduced state, probably reduced by 2 electrons from A ox , which is proposed to be {Ni d 2ϩ -Ni p 1ϩ -[Fe 4 S 4 ] 1ϩ }, has not yet been firmly established (10-11). The order of the addition of the substrates, Me, CO, and CoA, to the active site is also controversial, and several mechanisms have been proposed on the basis of biological and computational studies (12)(13)(14). On the other hand, synthetic studies that probe the reaction mechanisms are limited in number, although various thiolato-bridged dinuclear nickel complexes have been reported as A-cluster models (15-23).Proposed ACS mechanisms commonly involve the following steps: (i) methyl transfer from methylcobalamin to the reduced Ni p (0) [or Ni p (I)] site, (ii) CO insertion into the Ni p -Me bond, and (iii) formation of acetyl-CoA via the reductive elimination at the Ni p site (1-3, 7-14). These reactions had been studied by using mononuclear nickel complexes. CO insertion into the Ni-Me bonds of Ni(NS 3 R )Me [NS 3 R is N(CH 2 CH 2 SR) 3 ; R is i-Pr, t-Bu], investigated by Stavropoulos et al. (24) , resulted in the formation of acetylthioesters CH 3 C(O)SR and Ni(0) species in high yield upon treatment with CO. Likewise, the reaction of [Ni(bpy)(SR)(Me)] with Ͼ3 equiv of CO was found to yield [Ni(bpy)(CO) 2 ] and acetylthioesters (25). Before these reports, Kim et al. (26) had shown that the reaction of Ni(dppe-)(SAr)(Me) with CO generated CH 3 C(O)SAr. Recently, Rampersad et al. (27) demonstrated the acetylthioester formation in the reaction of Ni-Pd dinuclear complex, Ni(bme-daco)Pd(CO-)(COMe), with NaSMe. Eckert ...

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“…[1] However, due to the earlier reports of Cu-or Zn-containing structures, [2,3] attempts to synthesise structural models of the A-cluster have resulted in reports of several new heteronuclear clusters. [4][5][6][7][8][9][10][11] In most of these investigations, discrete mononuclear nickel complexes of tetradentate N 2 S 2 ligands have been used as building blocks, and their reactivity towards transition metals such as Fe, Ni, Cu, Zn, Ag, Pd and Hg have been studied. The nickel complexes can be considered to react as didentate S ligands.…”

Section: Introductionmentioning

confidence: 99%

“…(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) discrete NiCu or NiNi dinuclear complexes [4,5,8,11] or linear trinuclear Ni 3 or Ni 2 Cu complexes; [8,15] or they may bind to four different metal ions through µ 3 -S bridges in larger Ni 2 Cu 4 aggregates. [16] The nuclearity of the cluster and type of aggregate that is formed is largely dependent on the stoichiometry of the reactants and the presence or absence of coordinating anions.…”

Section: Introductionmentioning

confidence: 99%

Nickel Thiolate Complexes as Ligands for Copper and Zinc: Novel Additions to a Library of Binding Modes

et al. 2006

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The reactivity of the two nickel complexes [Ni(xbsms)] and [Ni(bsms) 2 ] [H 2 xbsms = α,αЈ-bis(4-mercapto-3,3-dimethyl-2-thiabutyl)-o-xylene; Hbsms = 4-mercapto-3,3-dimethyl-1-phenyl-2-thiabutane] towards copper iodide and zinc bromide has been investigated. The reactions yield novel aggregates of higher nuclearity with topologies that are different from previous reports; the nickel complexes in all cases can be considered as didentate S ligands. The X-ray structure of the novel octanuclear cluster [{Ni(bsms) 2 } 3 (CuI) 5 ] shows a unique arrangement in which the cis-NiS 2 SЈ 2 units act as didentate ligands to a trigonal-bipyramidal array of five Cu I ions. The tetranuclear structure of [{Ni(xbsms)CuI} 2 ] shows unprecedented asymmetric bridging of the thiolate sulfur atoms, with one of the thiolate groups binding to one copper

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Structure and electronic properties of an asymmetric thiolate-bridged binuclear complex: a model for the active site of acetyl CoA synthase

Cited by 43 publications

References 21 publications

Synthetic Analogues of the Active Site of the A-Cluster of Acetyl Coenzyme A Synthase/CO Dehydrogenase: Syntheses, Structures, and Reactions with CO

Synthetic Analogues of the Active Site of the A-Cluster of Acetyl Coenzyme A Synthase/CO Dehydrogenase: Syntheses, Structures, and Reactions with CO

Dinuclear nickel complexes modeling the structure and function of the acetyl CoA synthase active site

Nickel Thiolate Complexes as Ligands for Copper and Zinc: Novel Additions to a Library of Binding Modes

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