CO Binding to the FeMo Cofactor of CO-Inhibited Nitrogenase:  <sup>13</sup>CO and <sup>1</sup>H Q-Band ENDOR Investigation

Lee, Hong‐In; Cameron, Linda M.; Hales, Brian J.; Hoffman, Brian M.

doi:10.1021/ja9715096

Cited by 140 publications

(216 citation statements)

References 44 publications

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“…Several earlier studies have suggested two binding sites on FeMo cofactor. For example, it has been proposed that two CO molecules bind to FeMo cofactor in the high CO concentration inhibited state (29)(30)(31)(32)(33). Likewise, two acetylene binding sites have been implicated from studies combining kinetics and amino acid substitutions (31,34,35).…”

Section: Discussionmentioning

confidence: 99%

“…Several earlier studies revealed multiple inhibitor and substrate binding sites on FeMo-cofactor, including at least two binding sites for CO (29)(30)(31)(32)(33) and acetylene (31,34,35). Two adjacent binding sites can explain the earlier reports that two or three CO molecules can be reduced and coupled to form C2 and C3 hydrocarbon products (24,26).…”

Section: Co 2 Reduction To Chmentioning

confidence: 95%

See 1 more Smart Citation

Carbon dioxide reduction to methane and coupling with acetylene to form propylene catalyzed by remodeled nitrogenase

Yang

Moure

Dean

et al. 2012

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

108

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A doubly substituted form of the nitrogenase MoFe protein (α-70 Val→Ala , α-195 His→Gln ) has the capacity to catalyze the reduction of carbon dioxide (CO 2 ) to yield methane (CH 4 ). Under optimized conditions, 1 nmol of the substituted MoFe protein catalyzes the formation of 21 nmol of CH 4 within 20 min. The catalytic rate depends on the partial pressure of CO 2 (or concentration of HCO 3 − ) and the electron flux through nitrogenase. The doubly substituted MoFe protein also has the capacity to catalyze the unprecedented formation of propylene (H 2 C = CH-CH 3 ) through the reductive coupling of CO 2 and acetylene (HC≡CH). In light of these observations, we suggest that an emerging understanding of the mechanistic features of nitrogenase could be relevant to the design of synthetic catalysts for CO 2 sequestration and formation of olefins.is an abundant and stable form of carbon that is the product of respiration and burning of fossil fuels. As a result of these activities, the atmospheric concentration of CO 2 , a greenhouse gas, has been rising over the last century and contributing to global warming (1). There is strong interest in developing methods for sequestering CO 2 either by capturing it or by chemically converting it to valuable chemicals (2-5). Of particular interest are possible routes to reduction of CO 2 by multiple electrons to yield methanol (CH 3 OH) and methane (CH 4 ), which are renewable fuels (2). The reduction of CO 2 is difficult, with a limited number of reports of metal-based compounds able to catalyze these reactions (6-13). In biology, only a few enzymes are known to reduce CO 2 (14-18), and none of these can catalyze the eight electron reduction to CH 4 .The bacterial Mo-dependent nitrogenase enzyme catalyzes the multielectron/proton reduction of dinitrogen (N 2 ) to two ammonia (NH 3 ) at a metal cluster designated FeMo-cofactor [7Fe-9S-1Mo-1C-R-homocitrate] (Fig. 1) in a reaction that requires ATP hydrolysis and evolution of H 2 , with a minimal reaction stoichiometry shown in Eq. 1 (19)(20)(21)(22).Given that nitrogenase is effective at catalyzing the difficult multielectron reduction of N 2 , it was of interest to determine whether this enzyme might also catalyze the reduction of CO 2 to the level of CH 4 . Nitrogenase is known to have the capacity to reduce a variety of other small, relatively inert, doubly or triply bonded compounds, such as acetylene (HC≡CH) (19,23). It has been shown that an alternative form of nitrogenase, which contains V in place of Mo in the active site cofactor, has the remarkable capacity to reduce CO and couple multiple CO molecules, yielding short chain alkenes and alkanes such as ethylene (C 2 H 4 ), ethane (C 2 H 6 ), propylene (C 3 H 6 ), and propane (C 3 H 8 ) (24,25). In contrast, the Mo-nitrogenase is only able to reduce CO at exceedingly low rates (24). However, we have found that the MoFe protein can be remodeled by substitution of amino acid residues that provide the first shell of noncovalent interactions with the active site FeMo cofa...

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Section: Discussionmentioning

confidence: 99%

Section: Co 2 Reduction To Chmentioning

confidence: 95%

Carbon dioxide reduction to methane and coupling with acetylene to form propylene catalyzed by remodeled nitrogenase

Yang

Moure

Dean

et al. 2012

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

108

View full text Add to dashboard Cite

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“…As a result, some 2,000 non-fire-related CO-poisoning deaths occur annually in the United States (92). Human toxicity is attributed to the high affinity of CO for iron such that the oxygen capacity of hemoglobin is reduced, and the gas is broadly inhibitory for heme proteins and nonheme iron enzymes including hydrogenase (2,45,106) and nitrogenase (20,83,106). In light of its heme affinity, it is a biological irony that the primary endogenous source of CO in mammals is heme degradation catalyzed by multiple heme oxygenase activities in the cell.…”

Section: Sources and Biological Impacts Of Comentioning

confidence: 99%

“…First, as detailed below, the purified protein shows a significant response to CO. Second, the response of FixL to a variety of small-molecule ligands serves as a useful counterpoint to the extreme ligand specificity of CooA. Finally, because CO is a potent inhibitor of nitrogenase (20,83), the notion of a physiologically significant response by FixL to CO is not preposterous.…”

Section: Fixlmentioning

confidence: 99%

CO-Sensing Mechanisms

Roberts

Youn

Kerby

2004

Microbiol Mol Biol Rev

101

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Carbon monoxide (CO) has long been known to have dramatic physiological effects on organisms ranging from bacteria to humans, but recently there have a number of suggestions that organisms might have specific sensors for CO. This article reviews the current evidence for a variety of proteins with demonstrated or potential CO-sensing ability. Particular emphasis is placed on the molecular description of CooA, a heme-containing CO sensor from Rhodospirillum rubrum, since its biological role as a CO sensor is clear and we have substantial insight into the basis of its sensing ability

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“…Hoffman and coworkers have been able to demonstrate that CO can bind to iron sites on the FeMo-cofactor under turnover conditions through ingenious spectroscopic experiments utilizing isotopically substituted CO and cofactor (64). These studies have been interpreted in terms of multiple binding modes of the CO to the cofactor that vary in affinity and bonding interactions (65). CO binding to the MoFe-protein has also been monitored by stopped-flow infrared spectroscopy, which again indicates the binding of multiple COs to a metallocluster (66).…”

mentioning

confidence: 99%

Great Metalloclusters in Enzymology

Rees

2002

Annu. Rev. Biochem.

204

134

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Key Words metalloproteins, iron-sulfur clusters, nitrogenase, hydrogenase, carbon monoxide dehydrogenase, nitrous oxide reductase f Abstract Metallocluster-containing enzymes catalyze some of the most basic redox transformations in the biosphere. The reactions catalyzed by these enzymes typically involve small molecules such as N 2 , CO, and H 2 that are used to generate both chemical building blocks and energy for metabolic purposes. During the past decade, structures have been established for the iron-sulfur-based metalloclusters present in the molybdenum nitrogenase, the iron-only hydrogenase, and the nickel-carbon monoxide dehydrogenase, and for the coppersulfide-based cluster in nitrous oxide reductase. Although these clusters are built from interactions observed in simpler metalloproteins, they contain novel features that may be relevant for their catalytic function. The mechanisms of metallocluster-containing enzymes are still poorly defined and represent substantial and continuing challenges to biochemists, biophysicists, and synthetic chemists. These proteins also provide a window into the union of the biological and inorganic worlds that may have been relevant to the early evolution of biochemical catalysis. Annu. Rev. Biochem. 2002. 71:221-46 DOI: 10.1146 Copyright © 2002 by Annual Reviews. All rights reserved 221 0066-4154/02/0707-0221$14.00 Annu. Rev. Biochem. 2002.71:221-246 CONTENTS INTRODUCTIONAmong the most remarkable chemical transformations in biological systems are the oxidation-reduction reactions of some of the smallest molecules, including N 2 , CO, and H 2 . Redox processes involving these species not only generate basic chemical building blocks required by living organisms but can also generate the energy needed to fuel their metabolisms. Although binding sites of exquisite specificity for molecules ranging from small organic metabolites to enormous macromolecules can be constructed from the standard amino acids and nucleotides, these groups are poorly suited for binding and catalyzing the redox reactions of diatomic and similar molecules. Consequently, it is necessary to incorporate specialized metallocofactors into enzymes to provide the binding interactions for these small substrates, as well as to confer the catalytic capabilities necessary to achieve the desired transformations. Metalloclusters also provide a fascinating window into the union of the biological and inorganic worlds that may have arisen early in evolution to effect the metabolism of small molecules required to drive the energetic and growth needs of primitive organisms. Indeed, it has been proposed that before an RNA world could even exist, the central biochemical processes arose from a surface-based metabolism on the iron-sulfur-containing mineral pyrite (1). What may be the vestiges of this metabolism can perhaps still be perceived in these contemporary clusters.This review surveys the metalloclusters that have been structurally characterized in enzymes (Figure 1). Although the choice of clusters covered is partl...

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CO Binding to the FeMo Cofactor of CO-Inhibited Nitrogenase: ¹³CO and ¹H Q-Band ENDOR Investigation

Cited by 140 publications

References 44 publications

Carbon dioxide reduction to methane and coupling with acetylene to form propylene catalyzed by remodeled nitrogenase

Carbon dioxide reduction to methane and coupling with acetylene to form propylene catalyzed by remodeled nitrogenase

CO-Sensing Mechanisms

Great Metalloclusters in Enzymology

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CO Binding to the FeMo Cofactor of CO-Inhibited Nitrogenase: 13CO and 1H Q-Band ENDOR Investigation

Cited by 140 publications

References 44 publications

Carbon dioxide reduction to methane and coupling with acetylene to form propylene catalyzed by remodeled nitrogenase

Carbon dioxide reduction to methane and coupling with acetylene to form propylene catalyzed by remodeled nitrogenase

CO-Sensing Mechanisms

Great Metalloclusters in Enzymology

Contact Info

Product

Resources

About

CO Binding to the FeMo Cofactor of CO-Inhibited Nitrogenase: ¹³CO and ¹H Q-Band ENDOR Investigation