178,250 research outputs found
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
Bisson Family Photograph
No full textPhotograph of the Bisson Family: (front, center, l-r) Ted, Gertrude, and baby Andrew, Lewiston, Maine, c.1946.https://digitalcommons.usm.maine.edu/alice-bisson-barnes/1003/thumbnail.jp
Bisson Family Photograph (c. 1940)
No full textBisson Family, Lewiston, c.1940.
Seated, l-r: Jeanette, Josephine (mother). Standing:- Aurore, Louis, Theodore, Alphone, Patrick, Regina. The father, Evariste, had died earlier that year.https://digitalcommons.usm.maine.edu/alice-bisson-barnes/1013/thumbnail.jp
Different polypeptides of bovine heart cytochrome c oxidase are in contact with cytochrome c
No full textAbstractTwo water-soluble carbodiimides, differing in molecular dimensions, have been used to characterize the cytochrome c binding site of bovine heart cytochrome c oxidase. Several polypeptide components of the enzyme contain acidic residues which are modified by these reagents. Carboxyl groups present in subunit II, VII and polypeptide c, are protected from modification when cytochrome c, equimolar to oxidase, is added and they can cross-link to the substrate once activated by the carbodiimide. Comparison of the modification patterns suggest that the most reactive residues are located on subunit II and VII, the former being also more exposed. The data obtained indicate that eventhough subunit II plays the major role in binding cytochrome c, at least two other lower Mr polypeptides contribute to the cytochrome c binding domain
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..
Expression of cytochrome c oxidase during growth and development of Dictyostelium
No full textIn the slime mold Dictyostelium discoideum, the subunit composition of cytochrome c oxidase depends on oxygen that inversely regulates the concentrations of two alternative isoforms of the smallest enzyme subunit (Schiavo, G., and Bisson, R. (1989) J. Biol. Chem. 264, 7129-7134). In order to investigate their role in the Dictyostelium life cycle, the expression of the oxidase subunits was monitored during cell growth and development. The results obtained demonstrate that exponentially growing amoebae respond rapidly and precisely to hypoxia by switching the expression of the two isoforms and also by increasing the levels of the mRNAs of the different oxidase subunits in a highly coordinated process. During normal development the "hypoxic" subunit is not synthesized, but its level of expression appears to parallel the sensitivity to oxygen of development, rising steeply below 10% oxygen when the differentiation program is virtually blocked. Under these conditions, the expression of the alternative subunit isoform is essentially oxygen-insensitive. These findings suggest that the physiological relevance of the subunit switching concerns primarily the vegetative phase of growth, possibly as part of a more general mechanism evolved in order to evade conditions that do not allow development. Taken together, the data obtained offer an intriguing example of the fine control exerted on the expression of a key respiratory enzyme in a strictly aerobic organism
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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