Monomerization of cytochrome oxidase may be essential for the removal of subunit III

Finel, Moshe; Wikström, Mårten

doi:10.1111/j.1432-1033.1988.tb14259.x

Cited by 13 publications

(9 citation statements)

References 29 publications

(16 reference statements)

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“…Despite the fact that COIII can be easily lost during purification, it is most probably a stoichiometric component of the oxidase complex in situ (Haltia et al, 1988;Bolgiano et al, 1988). Studies on the oligomeric state of the enzyme have suggested that CORI resides in the interphase between the monomers (Finel and Wikstrom, 1988 to be monomeric Finel, 1989). Studies on the oligomeric state of the enzyme have suggested that CORI resides in the interphase between the monomers (Finel and Wikstrom, 1988 to be monomeric Finel, 1989).…”

Section: Discussionmentioning

confidence: 99%

“…Protein concentrations were measured according to Markwell et al (1978). SDS-PAGE, carried out using buffer system of Laemmli (1970) in 10-20% gradient acrylamide gels containing 5 M urea, and immunoblotting have been described by Finel and Wikstrom (1988). Paracoccus cytochrome aa3 was purified according to Bolgiano et al (1988) and Haltia et al (1988).…”

Section: Miscellaneousmentioning

confidence: 99%

“…This active site may reside approximately in the middle of the membrane dielectric (Holm et al, 1987;Wikstrom, 1988). Four electrons needed for this reaction are donated by cytochrome c on the outer surface of the membrane.…”

Section: Introductionmentioning

confidence: 99%

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Deletion of the gene for subunit III leads to defective assembly of bacterial cytochrome oxidase.

et al. 1989

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COIII is one of the major subunits in the mitochondrial and a bacterial cytochrome c oxidase, cytochrome aa3. It does not contain any of the enzyme's redox‐active metal centres and can be removed from the enzyme without major changes in its established functions. We have deleted the COIII gene from Paracoccus denitrificans. The mutant still expresses spectroscopically detectable enzyme almost as the wild‐type, but its cytochrome c oxidase activity is much lower. From 50 to 80% of cytochrome a is reduced and its absorption maximum is 2‐3 nm blue‐shifted. The EPR signal of ferric cytochrome a is heterogeneous indicating the presence of multiple cytochrome a species. Proteolysis of the membrane‐bound oxidase shows new cleavage sites both in COI and COII. DEAE‐chromatography of solubilized enzyme yields fractions that contain a COI + COII complex and in addition haem‐binding, free COI as well as free COII. The mutant phenotype can be complemented by introducing the COIII gene back to cells in a plasmid vector. We conclude that cytochrome oxidase assembles inefficiently in the absence of COIII and that this subunit may facilitate a late step in the assembly. The different oxidase species in the mutant represent either accumulating intermediates of the assembly pathway or dissociation products of a labile COI + COII complex and its conformational variants.

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Section: Discussionmentioning

confidence: 99%

Section: Miscellaneousmentioning

confidence: 99%

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Deletion of the gene for subunit III leads to defective assembly of bacterial cytochrome oxidase.

et al. 1989

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“…The binding of COIII to the other subunits appears to be sensitive to some detergents (e.g. dodecyldimethylamine N-oxide) and to alkaline pH (see Finel & Wikstrom, 1988). For instance, an incubation of the enzyme at pH 95 leads to the release of COIII.…”

Section: Subunit Himentioning

confidence: 99%

“…It has been postulated (Nalecz et al 1985;Finel & Wikstrom, 1988) that COIII The values are compiled from sedimentation equilibrium measurements. Minimal molecular weights are calculated from the amino acid sequences, assuming that the subunits are present in a 1:1 stoichiometry (Buse et al 1983;Kadenbach et al 1987).…”

Section: I I I I I I I I 1 I I I I I I I I I I I I I I I I I I I I mentioning

confidence: 99%

Structural features of cytochrome oxidase

Saraste

1990

Quart. Rev. Biophys.

405

330

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This article tries to be a compact summary of some recent research on cytochromecoxidase (EC 1.9.3.1), an important enzyme in membrane bioenergetics. Cytochrome oxidase is the terminal catalyst of the mitochondrial respiratory chain. It uses the electrons flowing through the chain to reduce oxygen molecules to water. Four electrons and four protons are consumed in the reduction of O2to two molecules of water (Fig. 1). Cytochrome oxidase contains four redoxactive metal centres. Two of these are copper atoms, two haem A groups. These four centres are employed in the dioxygen-binding site and in the electron-transferring pathways from cytochromec. The enzyme is also called cytochromeaa3, because the protein-bound haems are functionally and spectroscopically different.

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