The pathway of CO binding to cytochrome <i>c</i> oxidase Can the gateway be closed?

Hill, Bruce C.

doi:10.1016/0014-5793(94)01140-0

Cited by 20 publications

(15 citation statements)

References 23 publications

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“…In the reduced enzyme, carbon monoxide release and binding to iron of heme a 3 was associated with transient coordination to Cu B . Moreover, CO release from the reduced catalytic center is dramatically diminished when cyanide is present in solution (51). Altogether our results as well as published data (46 -51) suggest that Cu B is an obligatory site for the exit and entry of ligands to both the oxidized and the reduced binuclear center.…”

Section: Discussionsupporting

confidence: 78%

Ligand Trapping by Cytochrome c Oxidase

Parul

Palmer

Fabián

2010

Journal of Biological Chemistry

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Cytochrome c oxidase is a member of the heme-copper family of oxygen reductases in which electron transfer is linked to the pumping of protons across the membrane. Neither the redox center(s) associated with proton pumping nor the pumping mechanism presumably common to all heme-copper oxidases has been established. A possible conformational coupling between the catalytic center (Fe a3 3؉ -Cu B 2؉ ) and a protein site has been identified earlier from ligand binding studies, whereas a structural change initiated by azide binding to the protein has been proposed to facilitate the access of cyanide to the catalytic center of the oxidized bovine enzyme. Here we show that cytochrome oxidase pretreated with a low concentration of azide exhibits a significant increase in the apparent rate of cyanide binding relative to that of free enzyme. However, this increase in rate does not reflect a conformational change enhancing the rapid formation of a Fe a3 3؉ -CN-Cu B 2؉ complex. Instead the cyanide-induced transition of a preformed Fe a3 3؉ -N 3 -Cu B 2؉ to the ternary complex of Fe a3 3؉ -N 3 Cu B 2؉ -CN is the most likely reason for the observed acceleration. Significantly, the slow rate of azide release from the ternary complex indicates that cyanide ligated to Cu B blocks a channel between the catalytic site and the solvent. The results suggest that there is a pathway that originates at Cu B and that, during catalysis, ligands present at this copper center control access to the iron of heme a 3 from the bulk medium.

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Section: Discussionsupporting

confidence: 78%

Ligand Trapping by Cytochrome c Oxidase

Parul

Palmer

Fabián

2010

Journal of Biological Chemistry

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“…An outline of some of the proposed mechanisms is presented in Fig. 1 cytochrome aa 3 in vitro [55,56], and the disruption of oxidative metabolism via cytochrome oxidase may lead to the generation of oxygen free radicals [40,57]. Cellular respiration also may be impaired via inactivation of mitochondrial enzymes and impaired electron transport from oxygen radicals (ie, peroxynitrite) produced after CO exposure [40,58,59].…”

Section: Direct Cellular Toxicitymentioning

confidence: 98%

Carbon monoxide poisoning

Kao¹,

Nañagas²

2004

Emergency Medicine Clinics of North America

167

171

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“…Besides hemoglobin, CO binds to many hemecontaining proteins such as myoglobin, guanylyl cyclase, and cytochrome oxidase (Chance et al, 1970;Hill, 1994;Omaye, 2002;Kao and Nanagas, 2006). However, the affinity of CO for cytochrome oxidase is very low and this interaction would require a dose far exceeding the lethal dose of CO (Prockop and Chichkova, 2007).…”

Section: Mechanism Of Toxicitymentioning

confidence: 98%