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THE 2 OXYGEN-REGULATED SUBUNITS OF CYTOCHROME-C OXIDASE IN DICTYOSTELIUM-DISCOIDEUM DERIVE FROM A COMMON ANCESTOR
No full textThe two smallest polypeptide components of D. discoideum cytochrome c oxidase, whose alternative expression depends on oxygen concentration [Schiavo, G. and Bisson, R. (1989) J. Biol. Chem. 264, 7129-7134], have been partially sequenced. They show 45% homology and are isoforms of the same subunit, which must be encoded on two different genes
Inhibition of the synthesis of a cytochrome‐c‐oxidase subunit isoform by antisense RNA
No full textTo investigate the role of subunit VIIe, an oxygen‐regulated subunit isoform of Dictostelium discoideum cytochrome‐c oxidase, the full‐length cDNA was inserted into an expression vector under the control of an actin promoter in the sense and antisense orientation. The DNA constructs were used for stable transformation of the slime mold amoebae. In most of the 28 antisense clones tested, the concentration of cytochrome‐c oxidase was lowered compared to the wild type, while no significant changes were found in the sense mutants. Antisense RNA was abundantly expressed, leading to a drastic reduction of the steady‐state level of the endogenous subunit VIIe mRNA, which was decreased up to 20–30% the level observed in parent cells. In these transformants, the amount of the target polypeptide and cytochrome c oxidase was 40–50% and 60–70% of control, respectively. A similar decrease was found in the level of the remaining nuclear and mitochondrial subunits. Unexpectedly, these changes affecte..
Cytochrome c oxidase from the slime mold Dictyostelium discoideum: Purification and characterization
No full textCytochrome c oxidase was purified from growing cells of the slime mold Dictyostelium discoideum by a procedure based on hydrophobic and affinity chromatography. A highly pure (13.4-15 nmol of heme a/mg of protein) and active (turnover number = 280-330 s-1, when assayed polarographically with the slime mold cytochrome c) enzyme preparation was obtained. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, under conditions where the 12 polypeptide components of the bovine enzyme are resolved, shows that the amoeba oxidase consists of six subunits with molecular masses of 55, 29.5,19,13,11, and 5.7 kDa. A polypeptide with the characteristics of the eukaryotic subunit III is missing, and N,N-dicyclohexyl-carbodiimide, a specific reagent for this component, labels subunit I. Under controlled conditions and even at physiological pH, the single subunit present at Mr <10000 can be selectively removed from the complex. Hydrophobic photolabeling suggests that with the mitochondrial subunits I and II only subunit IV among the nuclear coded polypeptides is in contact with lipids. © 1985 American Chemical Society.
INDEX KEYWORDS: cytochrome c oxidase; dicyclohexylcarbodiimide, dictyostelium discoideum; enzyme subunit; fungus; nonhuman; priority journal
CHEMICALS/CAS: cytochrome c oxidase, 72841-18-0, 9001-16-5; dicyclohexylcarbodiimide, 538-75-
Hydrophobic photolabelling of the yeast cytochrome c oxidase subunits in contact with lipids
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ATP induces conformational changes in mitochondrial cytochrome c oxidase. Effect on the cytochrome c binding site.
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