REGULATION OF YEAST MITOCHONDRIAL PROTEIN SYNTHESIS.
Item
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Title
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REGULATION OF YEAST MITOCHONDRIAL PROTEIN SYNTHESIS.
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Identifier
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AAI8401930
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identifier
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8401930
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Creator
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FINZI, ERIC.
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Contributor
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Prof. Diana S. Beattie
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Date
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1983
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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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Biology, General
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Abstract
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Protein synthesis in isolated yeast mitochondria incubated in the presence of optimal amounts of GTP is stimulated 2-fold by addition of dialyzed postpolysomal supernatant (S-150) from either yeast, rat liver, or rat skeletal muscle. S-150's isolated from either glucose-repressed or stationary phase yeast cells had considerably lower stimulatory activity than S-150 isolated from midlog phase cells. Cycloheximide treatment of rats decreased the amino acid incorporation rate by isolated liver mitochondria and lowered the stimulatory activity of the corresponding liver S-150 in comparison with control liver supernatant.;A partial purification of the cytosolic factors which stimulate yeast mitochondrial protein synthesis has been accomplished by chromatography of yeast S-150 on Sephadex G-50. Most of the stimulatory activity eluted in a peak with a molecular weight of 2000 or less. Stimulation of mitochondrial protein synthesis by the low molecular weight activator fraction was insensitive to cycloheximide, sensitive to chloramphenicol and trypsin, and proportional to the concentration of protein added. Mitochondrial protein synthesis in the absence of activator ceased after 20 min, while that in the presence of activator continued for 40 min. Analysis of the products of the stimulated mitochondrial protein synthesis by dodecylsulfate polyacrylamide gel electrophoresis revealed that the activator increased equally the labeling of all products. These results suggest that cytoplasmic levels of low molecular weight factors present in the cytosol regulate mitochondrial protein synthesis in vivo.;Yeast mitochondrial protein synthesis shows biphasic Arrhenius plots both in vivo and in vitro, with a two-fold increase in the activation energy below the transition temperature, suggesting a functional association between mitochondrial protein synthesis and the inner membrane. Gel electrophoresis of mitochondrial translation products labeled in vivo revealed that the same proteins are synthesized and then inserted into the membrane above and below the transition temperature of the membrane.;The rate of leucine uptake into mitochondria was decreased at least five-fold in the presence of chloramphenicol, suggesting that leucine is used mainly for protein synthesis. Under conditions where the membrane potential was dissipated but matrix ATP levels high, uptake was inhibited, suggesting that the membrane potential is required for leucine transport which may occur by an active transport mechanism.
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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
