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Vectorial nature of redox Bohr effects in bovine heart cytochrome c oxidase
No full textThe vectorial nature of redox Bohr effects (redox-linked pK shifts) in cytochrome c oxidase from bovine heart incorporated in liposomes has been analyzed. The Bohr effects linked to oxide-reduction of heme a and CUB display membrane vectorial asymmetry. This provides evidence for involvement of redox Bohr effects in the proton pump of the oxidase
Factors affecting the H+/e- stoichiometry in mitochondrial cytochrome c oxidase: influence of the rate of electron flow and transmembrane delta pH.
No full textA study is presented of the factors affecting the H+/e- stoichiometry of the proton pump of mitochondrial cytochrome c oxidase, isolated and reconstituted in phospholipid vesicles (COV). Under lever flow conditions, i.e., in the absence of a transmembrane ΔμH+, the H+/e- ratio, obtained from spectrophotometric measurements of the initial rates of electron flow and H+ release specifically elicited by cytochrome c, varied from around 0 to 1, depending on the actual rate of electron flow through the oxidase. At steady state the H+/e- ratio for the oxidase was specifically depressed by the transmembrane ΔpH. The study of the H+/e- ratio of the pump was complemented by an analysis of the redox pattern of cytochrome c, Cu(A), and heme a. From both sets of results and recent structural data from other groups, it is concluded that the dependence of the H+/e- ratio on the rate of electron flow through the oxidase and transmembrane ΔpH is associated with the possible occurrence of two electron transfer pathways in cytochrome c oxidase, a coupled one (cyt c → Cu(A) → heme a → heme a3-Cu(B)) and a decoupled one (cyt c → Cu(A) → heme a3-Cu(B)). The contributions of the two pathways, differently affected by kinetics and thermodynamic factors, will determine the actual H+/e- ratio of the pump. A possible role of heme a in the proton pump and the physiological implication of the variable H+/e- ratio in the oxidase are discussed
The cytochrome chain of mitochondria exhibits variable H+/e− stoichiometry
No full textAbstractA study is presented of the ←H+/e− stoichiometry for H+ pumping by the cytochrome chain in isolated rat liver mitochondria under level-flow and steady-state conditions. It is shown that the ←H+/e− stoichiometry for the cytochrome chain varies under the influence of the flow rate and transmembrane ΔμH+. The rate-dependence is shown to be associated with cytochrome c oxidase, whose ←H+/e− ratio varies from 0 to 1, whilst the ←H+/c− ratio for the span covered by cytochrome c reductase is invariably 2
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Role of nuclear-encoded subunits of mitochondrial cytochrome c oxidase in proton pumping revealed by limited enzymatic proteolysis.
No full textpH dependence of proton translocation in the oxidative and reductive phases of the catalytic cycle of cytochrome c oxidase. The role of H2O produced at the oxygen-reduction site.
No full textProtonmotive activity of cytochrome c oxidase: control of oxidoreduction of the heme centers by the protonmotive force in the reconstituted beef heart enzyme.
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