THE ROLE OF CYTOCHROME B IN THE PROCESSING OF THE SUBUNITS OF COMPLEX III IN THE YEAST MITOCHONDRIA.
Item
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Title
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THE ROLE OF CYTOCHROME B IN THE PROCESSING OF THE SUBUNITS OF COMPLEX III IN THE YEAST MITOCHONDRIA.
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Identifier
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AAI8611381
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identifier
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8611381
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Creator
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SEN, KEYA GUPTA.
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Contributor
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Diana S. Beattie
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Date
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1986
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Biochemistry
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Abstract
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The work described in this dissertation deals with the effect of cytochrome b on the biogenesis and assembly of the subunits of complex III in the mitochondrial membrane of the yeast Saccharomyces cerevisiae. The cytochrome b - mutants (Box mutants) of S. cerevisiae form an excellent system to study such a role of cytochrome b. The steady state levels, the kinetics of synthesis and the assembly of the nuclear encoded subunits of complex III have been investigated and compared in both the Box mutants and the wild type parental cells. Thus when mitochondria from wild type and four mutant strains were analyzed by immunoblotting and immunoprecipitation techniques, using specific antisera, the two core proteins and the iron-sulfur protein were decreased 50% or more in the mitochondria from the mutants as compared to the wild type. By contrast, the amounts of cytochrome c(,1) in the mitochondria, as determined both spectroscopically and immunologically, were not affected by the absence of cytochrome b. Pulse labeling of the cells with (('35)S) methionine in the presence of CCCP showed the accumulation of the precursors to the core protein I and the iron-sulfur protein in similar amounts in the mutant Box 6-2 and the wild type cells. Synthesis of the iron-sulfur protein and the cytochrome c(,1) by in vitro translation of mRNA isolated from wild type and mutant Box 6-2 in a rabbit reticulocyte lysate system, also confirmed that the synthesis of the nuclear encoded subunits was not affected in the mutants. Pulse labeling of the cells in the absence of CCCP and subsequent chase with cold methionine, however, showed much less of the mature subunits of core protein I and the iron-sulfur protein in the mitochondria of the mutant cells relative to the wild type. Import of radiolabeled precursors, synthesized in vitro, into isolated mitochondria from the parental and the mutant strains indicated that less amounts of the iron-sulfur protein precursor was processed to the mature form in the mutant mitochondria of Box 6-2. Processing of the precursor of cytochrome c(,1) into isolated mitochondria, remained unaffected in the mutant cells and similar amounts of the intermediate and the mature form of the subunit was found in the mitochondria of both strains. These results indicate that cytochrome b is necessary for the proper processing of certain subunits of complex III.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Biomedical Sciences
