THE ROLE OF HEME IN THE BIOGENESIS AND ASSEMBLY OF MITOCHONDRIAL COMPLEX III IN YEAST CELLS.
Item
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Title
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THE ROLE OF HEME IN THE BIOGENESIS AND ASSEMBLY OF MITOCHONDRIAL COMPLEX III IN YEAST CELLS.
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Identifier
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AAI8508711
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identifier
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8508711
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Creator
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LIN, CHING-I PATSY.
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Contributor
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Diana S. Beattie
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Date
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1985
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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 purpose of my thesis was to investigate the role of heme in the biogenesis and assembly of mitochondrial complex III in yeast cells using a mutant strain yeast that lacks ALA-synthase. The purified complex III from yeast contains 8-10 protein subunits including two core proteins, apocytochromes b and c(,1) and the Rieske's iron-sulfur protein. The results obtained from this study indicated that heme exert diverse effects on the biogenesis of different hemoproteins.;Using the 'Western' immunotransfer and the immunoprecipitation technique, the two core proteins, apocytochrome b and the Rieske's iron-sulfur protein of complex III were found to be present in the mitochondria of heme-deficient yeast cells; however, the apocytochrome c(,1) was found to be present as the intermediate form in these heme-deficient yeast cells. Electron paramagnetic resonance signals due to all mitochondrial iron-sulfur clusters were found to be absent in these heme-deficient cells. Hence, heme governs the formation of yeast mitochondrial iron-sulfur cluster in yeast cells.;The orientation of complex III subunits in the mitochondrial membrane of the wild-type yeast cells was studied by a protein labeling technique. Results from such labeling experiments revealed that the two core proteins and the apocytochrome b span the membrane while apocytochrome c(,1) and the Rieske's protein are exposed on the cytosolic surface of the inner mitochondrial membrane. A model of the topography of complex III was deduced based on results of this study and from other complex III enzymatic studies.;In order to study the role of heme in the orientation of the complex III subunits in the membrane, parallel studies of protease digestion and immunoprecipitation followed by polyacrylamide gel electrophoresis were performed on mitoplasts from wild-type and heme-deficient mutant cells. Results from this study indicated that the two core proteins, apocytochrome b and the intermediate form of apocytochrome c(,1) have similar orientations in the membrane in wild-type and heme-deficient mutant yeast cells. However, the Rieske's iron-sulfur protein is more imbedded in the membrane in heme-deficient cells. Therefore, heme also governs the assembly of the mitochondrial iron-sulfur clusters in yeast cells.
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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
