| NAD turnover and utilisation of metabolites for RNA synthesis in a reaction sensing the redox state of the cytochrome b6f complex in isolated chloroplasts. | |
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MedLine Citation:
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PMID: 7505745 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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NAD is normally regarded as a redox molecule or as the substrate for ADP-ribosylation reactions. In this study, we describe the rapid metabolism of NAD by Percoll-gradient-purified lettuce chloroplasts and show that the adenine moiety can be incorporated into RNA in a dark-activated reaction that senses the redox state of the cytochrome b6f complex. Isolated chloroplasts rapidly metabolised radiolabelled NAD+ to 5'-AMP (within seconds) and adenosine during a 60-min incubation in vitro; the products were analysed by high-performance liquid chromatography. No radiolabelled ADP-ribose was detected. Radioactivity was incorporated into trichloroacetic-acid-insoluble material during this period, with approximately 2-4-fold more incorporation occurring in the dark. Most of this radiolabel was rendered acid-soluble by dilute alkaline digestion at 37 degrees C, yielding an approximately equal mixture of 2'-AMP and 3'-AMP, and by RNase digestion, identifying the acid-insoluble radioactive material as RNA. Protein-bound ADP-ribose would have yielded 5'-AMP and/or oligomeric/polymeric ADP-ribose after alkali digestion. The utilisation of NAD metabolites for RNA synthesis was restricted to the thylakoid compartment of the chloroplast. The use of a variety of electron-transport inhibitors such as 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone, bromanil (tetrabromo-1,4-benzoquinone), electron donors (dithiothreitol), electron acceptors (ferricyanide) and an uncoupler showed that the incorporation of radiolabel from NAD into acid-insoluble material was favoured when the cytochrome b6f complex was in the oxidised state (as pertaining to incubations in the dark). |
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Authors:
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C K Pearson; S B Wilson; R Schaffer; A W Ross |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: European journal of biochemistry / FEBS Volume: 218 ISSN: 0014-2956 ISO Abbreviation: Eur. J. Biochem. Publication Date: 1993 Dec |
Date Detail:
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Created Date: 1994-02-03 Completed Date: 1994-02-03 Revised Date: 2007-07-23 |
Medline Journal Info:
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Nlm Unique ID: 0107600 Medline TA: Eur J Biochem Country: GERMANY |
Other Details:
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Languages: eng Pagination: 397-404 Citation Subset: IM |
Affiliation:
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Department of Molecular and Cell Biology, University of Aberdeen, Scotland. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Chloroplasts
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enzymology* Chromatography, High Pressure Liquid Cytochromes / chemistry, metabolism* Cytochromes f Electron Transport / drug effects Hydrogen-Ion Concentration Kinetics Light NAD / metabolism* Oxidation-Reduction RNA / biosynthesis* Radioisotopes |
| Chemical | |
Reg. No./Substance:
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0/Cytochromes; 0/Radioisotopes; 53-84-9/NAD; 63231-63-0/RNA; 9035-46-5/Cytochromes f |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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