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Biomedical subjects

J Mary

Publications and source records attributed to J Mary.

11 recordsLinked to original sources
PubMed2004

Biological detection of low radiation doses by combining results of two microarray analysis methods.

The accurate determination of the biological effects of low doses of pollutants is a major public health challenge. DNA microarrays are a powerful tool for investigating small intracellular changes. However, the inherent low reliability of this technique, the small number of replicates and the lack of suitable statistical methods for the analysis of such a large number of attributes (genes) impair accurate data interpretation. To overcome this problem, we combined results of two independent analysis methods (ANOVA and RELIEF). We applied this analysis protocol to compare gene expression patterns in Saccharomyces cerevisiae growing in the absence and continuous presence of varying low doses of radiation. Global distribution analysis highlights the importance of mitochondrial membrane functions in the response. We demonstrate that microarrays detect cellular changes induced by irradiation at doses that are 1000-fold lower than the minimal dose associated with mutagenic effects.

Analysis of Variance↗
PubMed2001

Rat peptide methionine sulphoxide reductase: cloning of the cDNA, and down-regulation of gene expression and enzyme activity during aging.

Peptide methionine sulphoxide reductase (PMSR, EC 1.8.4.6), the msrA or pmsR gene product, is a ubiquitous enzyme catalysing the reduction of methionine sulphoxide to methionine in proteins. Decreased expression and/or activity of the PMSR with age could explain, at least in part, the accumulation of oxidized protein observed upon aging. To test this hypothesis, the rat pmsR cDNA was cloned and sequenced. The recombinant protein was expressed, its catalytic activity checked with a synthetic substrate and polyclonal antibodies were raised against recombinant PMSR. The expression of the pmsR gene and protein as well as its catalytic activity were then analysed as a function of age in the rat brain and in two organs that express the most PMSR, liver and kidney. It appears that pmsR gene expression decreases with age in liver and kidney as early as 18 months, whereas protein level and protein activity are reduced in the three organs at the very end of the life of the rat (26 months). These results suggest that the down-regulation of PMSR can contribute to the accumulation of oxidized protein that has been associated with the aging process.

Aging↗
PubMed1999

Isolation and characterization of a protein with high affinity for DNA: the glutamine synthetase of Thermus thermophilus 111.

In a search of proteins from the thermophilic bacterium Thermus thermophilus 111 with a high affinity for DNA, the selected protein from this screening appears to be the glutamine synthetase (GS). The purified product gives one band in SDS-polyacrylamide gel electrophoresis (53,700 Da). The N-terminal 32 residues have been identified and present an homology of 80% with the glutamine synthetase of Bacillus subtilis and 76% with that of Thermotoga maritima. The protein displays the characteristic dodecameric structure of the eubacteria glutamine synthetase. From a detailed study of the interaction of this protein with DNA by dark-field electron microscopy and agarose gel electrophoresis, it is concluded that double-stranded DNA wraps the protein by a full turn of 150 bp length. An even number of GS molecules bound to a closed relaxed plasmid DNA does not alter its null topology. By using an inverted dimer DNA fragment, which contains twice a curved kinetoplast DNA insert in its central part, it is shown that DNA curvature rules the order in which GS binds to the DNA. DNA ends are also sites of high affinity for the GS. Supercoiling does not favor the binding of GS to the DNA with the exception of the apices that are by essence bent regions. By saturating a DNA molecule with GS one obtains a novel characteristic scalloped configuration in which the DNA undulates from one GS to the next. The DNA is condensed at least three times in these structures. By increasing the ratio of GS to DNA in solution the resulting material migrates as discrete bands relative to the free DNA in an agarose gel. By gel retardation and EM statistical distribution analysis of GS within the complexes, an average affinity constant of 10(7) M-1 was obtained. The potential implications of this novel interaction of the glutamine synthetase with DNA for the regulation of its own gene are briefly discussed.

Amino Acid Sequence↗
PubMed1997

Posttranslational modifications of axonemal tubulin.

Axonemal tubulin exhibits a high degree of heterogeneity mostly due to several posttranslational modifications (PTM). The aim of this work was to chemically characterize the different PTM occurring in the C-terminal tail of axonemal tubulin purified from sea urchin, Paracentrotus lividus, spermatozoa. After its purification, tubulin was enzymatically cleaved. The C-terminal peptides were chromatographically isolated, first by anion exchange and then by reverse-phase HPLC. Peptides were characterized by their sequence, determined by Edman degradation, and by their mass, determined by MALDI-TOF/MS. The two major conclusions are that the majority of the isolated C-terminal peptides were unmodified and that polyglycylation and polyglutamylation can occur simultaneously on one molecule of alpha-tubulin.

Amino Acid Sequence↗
PubMed1996

Posttranslational modifications in the C-terminal tail of axonemal tubulin from sea urchin sperm.

After proteolytic digestion of sperm tubulin from sea urchin Paracentrotus lividus, C-terminal peptides were isolated by chromatographic separations. The peptides were analyzed by Edman degradation and matrix-assisted laser desorption/ionization-time of flight mass spectrometry. About 70% of the isolated C-terminal peptides were unmodified. The remaining modified peptides have undergone a combination of numerous posttranslational modifications generating significant heterogeneity of sperm tubulin. alpha-Tubulin is modified by detyrosylation, release of the penultimate glutamate, polyglutamylation, and polyglycylation. Glycylation and glutamylation can coexist within one alpha-tubulin isoform. beta-Tubulin undergoes polyglycylation but was not observed to be polyglutamylated. The number of units posttranslationally added reaches 11 and 12 glycyl units on beta- and alpha-tubulin, respectively. This is different from the polyglycylation of axonemal tubulin in Paramecium cilia where up to 40 added glycyl units were observed both on alpha- and beta-tubulin.

Amino Acid Sequence↗
PubMed1996

Structure of the C-terminal tail of alpha-tubulin: increase of heterogeneity from newborn to adult.

A combination of posttranslational modifications contributes to the high heterogeneity of brain tubulin in mammals. In this report, the structures of the detyrosinated carboxy-terminal peptides of alpha-tubulin from newborn and adult mouse brain were compared. The heterogeneity of these carboxy-terminal peptides was observed to increase from newborn to adult brain tubulin. The major part of this increased heterogeneity is due to the post-translational excision of Glu450, which makes alpha-tubulin nontyrosinatable (delta-2 tubulin). The structures of the polyglutamyl side chain of the bi- and triglutamylated peptides were analyzed in this work. In polyglutamylation of alpha-tubulin, the first glutamyl residue can only be amide-linked to the gamma-carboxyl group of Glu445, but the additional residues may be linked either to the gamma- or to the alpha-carboxyl groups of the preceding one. By optimized reverse-phase separations and comparison with synthetic peptides corresponding to all possible linkages for the biglutamylated (gamma 1 alpha 2, gamma 1 gamma 2) and triglutamylated (gamma 1 alpha 2 alpha 3, gamma 1 gamma 2 gamma 3, gamma 1 alpha 2 gamma 3, gamma 1 gamma 2 alpha 3, gamma 1 gamma 2 alpha 2) tubulin peptides, it was possible to conclude that the mode of linkage connecting the second and third additional glutamyl residues corresponds mostly to alpha-bond structures, for both newborn and adult mice.

Aging↗
PubMed1994

Class I and IVa beta-tubulin isotypes expressed in adult mouse brain are glutamylated.

Several types of post-translational modifications contribute to the high level of tubulin heterogeneity in the brain. An important modification is glutamylation of the major brain-specific isotypes, such as class Ia/b of alpha-tubulin and classes II and III of beta-tubulin. Here we describe experiments to determine if additional, minor tubulin isotypes, expressed in adult mouse brain, could also be glutamylated. Purified tubulin from adult mouse brain was cleaved with thermolysin. Proteolytically released carboxy-terminal peptides of both alpha- and beta-tubulin were isolated by sequential anion exchange and reverse-phase column-chromatography. Anionic peptides were then characterized by amino acid sequencing and mass spectrometry. We show that brain-specific class IVa and constitutive class I beta-tubulin isotypes can be glutamylated, at Glu434 and Glu441, respectively.

Amino Acid Sequence↗
PubMed1992

The nurse.

Explore the source record for details and available documents.

Humans↗
PubMed1977

[Evidence of an excretion of uric acid by a caecal pouch in the rabbit (author's transl)].

Uric acid was estimated in the blood plasma, the caecal content, and in the lumen of a caecal pouch in operated rabbits. It was also histochemically detected in the caecal wall. A non negligible excretion of uric acid through the perfused caecal pouch was demonstrated. There was also an accumulation of amorphous uric acid in the enterocytes, probably due to the absence of intestinal transit, and of microorganism's uricase.

Animals↗