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R Poulson

Publications and source records attributed to R Poulson.

At least 19 recordsLinked to original sources
PubMed1999

The mouse Aire gene: comparative genomic sequencing, gene organization, and expression.

Mutations in the human AIRE gene (hAIRE) result in the development of an autoimmune disease named APECED (autoimmune polyendocrinopathy candidiasis ectodermal dystrophy; OMIM 240300). Previously, we have cloned hAIRE and shown that it codes for a putative transcription-associated factor. Here we report the cloning and characterization of Aire, the murine ortholog of hAIRE. Comparative genomic sequencing revealed that the structure of the AIRE gene is highly conserved between human and mouse. The conceptual proteins share 73% homology and feature the same typical functional domains in both species. RT-PCR analysis detected three splice variant isoforms in various mouse tissues, and interestingly one isoform was conserved in human, suggesting potential biological relevance of this product. In situ hybridization on mouse and human histological sections showed that AIRE expression pattern was mainly restricted to a few cells in the thymus, calling for a tissue-specific function of the gene product.

Amino Acid Sequence↗
PubMed1977

Effects of lipids on the activity of ferrochelatase.

Removal of lipids from submitochondrial particles or detergent-solubilized mitochondrial preparations of rat liver resulted in a 90% loss of ferrochelatase (protochemeferro-lyase, EC 4.99.1.1) activity. The addition of either a fatty acid or phospholipid restored enzyme activity; the extent of reactivation being correlated with the degree of unsaturation of the fatty acid or acyl chain and independent of the polar head group of the phospholipid, Arrhenius plots of the ferrochelatase activities of submitochondrial particles and detergent-solubilized mitochondrial preparations showed transition temperatures of 37 and 28.5 degrees C, respectively. Ferrochelatase of submitochondrial particles or detergent-solubilized preparations had an absolute requirement for Ca2+. The ferrous salt of oxalic acid, a Ca2+ chelator, was a very poor substrate for these preparations. In contrast, ferrochelatase activities of fatty acid- or lipid-supplemented acetone extracts of these preparations were not dependent on the presence of Ca2+ and ferrous oxalate served as substrate for these extracts.20

Animals↗
PubMed1976

The enzymic conversion of protoporphyrinogen IX to protoporphyrin IX in mammalian mitochondria.

Protoporphyrinogen oxidase, an enzyme which catalyzes the oxidation of protoporphyrinogen IX to protoporphyrin IX in yeast cells, has been found in several mammalian tissues. It has been extracted from rat liver mitochondria by sonication in the presence of salt and detergent and partially purified. The enzyme is similar in many respects to yeast protoporphyrinogen oxidase. Based on its behavior on Sephadex G-200 the molecular weight of the enzyme is approximately 35,000. Catalysis by protoporphyrinogen oxidase was specific for proteoporphyrinogen IX (apparent Km of 11 muM) and proceeded maximally at pH 8.6 to 8.7. The effect of temperature on enzyme activity plotted according to Arrhenius gave a value of E of 9,100 calories per mol. Enzyme activity was inhibited in the presence of high salt concentrations and temperatures above 45 degrees. Oxygen was essential for protoporphyrinogen oxidase activity and an alternative elevtron acceptor has not yet been found. No requirement for a metal or other cofactor could be demonstrated. The presence of monothiol groups was indicated; however, it is not known whether the thiol groups are involved directly in the binding of substrate to the enzyme.

Animals↗
PubMed1976

The regulation of heme biosynthesis.

Changes in the levels of the heme biosynthetic enzymes were studied in cells and protoplasts of Saccharomyces cerevisiae during glucose derepression and respiratory adaptation. On aerobic or anaerobic glucose derepression or in the presence of 3', 5' cyclic AMP the levels of beta-aminolevulinic acid dehydratase, protoporphyrinogen oxidase and ferrochelatase increased whereas the levels of the enzymes catalysing the reactions from porphobilinogen to protoporphyrinogen IX remained constant. In contrast, the level of beta-aminolevulinic acid synthetase decreased during aerobic glucose derepression and in the presence of 3', 5' cyclic AMP, but it remained unchanged during anaerobic derepression. The heme content of the cells increased during aerobic glucose derepression but no increase was observed during anaerobic derepression of the cells. It is concluded that, in yeast, the inhibitory effect of anaerobiosis on heme synthesis is due, at least in part, to the requirement for oxygen in the oxidation of protoporphyrinogen IX, and that the effect of glucose on heme biosynthesis is mediated via glucose repression of protoporphyrinogen oxidase and possibly ferrochelatase.

5-Aminolevulinate Synthetase↗
PubMed1975

The enzymic conversion of protoporphyrinogen IX to protoporphyrin IX. Protoporphyrinogen oxidase activity in mitochondrial extracts of Saccharomyces cerevisiae.

The oxidation of protoporphyrinogen IX to protoporphyrin IX in yeast cells is enzyme-dependent. The enzyme, protoporphyrinogen oxidase, associated with purified mitochondria isolated from Saccharomyces cerevisiae was solubilized by sonic treatment in the presence of detergent and partially purified. The molecular weight of the enzyme was 180,000 plus or minus 18,000. The purified preparation could be stored at -20 degrees in the presence of 20% glycerol for several months without loss of activity. Enzyme activity was destroyed by heating above 40 degrees and by proteolytic digestion and irreversible inactivation occurred outside the pH range of 4.0 to 9.5. The pH optimum of the enzymic reaction was 7.45 and the value of the Michaelis constant was approximately 4.8 muM. Protoporphyrinogen oxidase did not catalyse the oxidation of coproporphyrinogen I or III or uroporphyrinogen I or III and the rate of enzymic oxidation of mesoporphyrinogen IX was less than 20% of that observed with protoporphyrinogen IX. The presence of thiol groups in the enzyme system was indicated but no metal ion or other cofactor requirement was demonstrated. Enzyme activity was insensitive to cyanide, 2,4-dinitrophenol, and azide whereas it was inhibited in the presence of Cu-2+ or Co-2+ ions, high ionic strength, heme, or hemin.

Acetates↗