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Y Hathout

Publications and source records attributed to Y Hathout.

12 recordsLinked to original sources
PubMed2000

Kurstakins: a new class of lipopeptides isolated from Bacillus thuringiensis.

A novel class of lipopeptides was isolated from Bacillus thuringiensis kurstaki HD-1. Four compounds (1-4) were separated by high-performance liquid chromatography and their primary structures determined using a combination of chemical reactions and mass spectrometry. The four lipopeptides were found to have the same amino acid sequence, Thr-Gly-Ala-Ser-His-Gln-Gln, but different fatty acids. The fatty acyl chain is linked to the N-terminal amino acid residue via an amide bond. Each lipopeptide has a lactone linkage between the carboxyl terminal amino acid and the hydroxyl group in the side chain of the serine residue. Antifungal activity was demonstrated against Stachybotrys charatum.

Amino Acids↗
PubMed2000

Rapid characterization of spores of Bacillus cereus group bacteria by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry.

Matrix-assisted laser desorption-ionization (MALDI) time-of-flight mass spectrometry was used to characterize the spores of 14 microorganisms of the Bacillus cereus group. This group includes the four Bacillus species B. anthracis, B. cereus, B. mycoides, and B. thuringiensis. MALDI mass spectra obtained from whole bacterial spores showed many similarities between the species, except for B. mycoides. At the same time, unique mass spectra could be obtained for the different B. cereus and B. thuringiensis strains, allowing for differentiation at the strain level. To increase the number of detectable biomarkers in the usually peak-poor MALDI spectra of spores, the spores were treated by corona plasma discharge (CPD) or sonicated prior to MALDI analysis. Spectra of sonicated or CPD-treated spores displayed an ensemble of biomarkers common for B. cereus group bacteria. Based on the spectra available, these biomarkers differentiate B. cereus group spores from those of Bacillus subtilis and Bacillus globigii. The effect of growth medium on MALDI spectra of spores was also explored.

Bacillus cereus↗
PubMed1999

Identification of Bacillus spores by matrix-assisted laser desorption ionization-mass spectrometry.

Unique patterns of biomarkers were reproducibly characterized by matrix-assisted laser desorption ionization (MALDI)-mass spectrometry and were used to distinguish Bacillus species members from one another. Discrimination at the strain level was demonstrated for Bacillus cereus spores. Lipophilic biomarkers were invariant in Bacillus globigii spores produced in three different media and in B. globigii spores stored for more than 30 years. The sensitivity was less than 5,000 cells deposited for analysis. Protein biomarkers were also characterized by MALDI analysis by using spores treated briefly with corona plasma discharge. Protein biomarkers were readily desorbed following this treatment. The effect of corona plasma discharge on the spores was examined.

Bacillus↗
PubMed1996

Cross-linking of human placenta pi class glutathione S-transferase dimer by chlorambucil.

Interaction of chlorambucil and the glutathione-depleted human placenta pi class glutathione S-transferase (pi GST) results in the formation of a complex between the drug and the protein at physiological pH. This complex is not formed in the presence of glutathione or S-hexylglutathione. Molecular mass measurement of the reaction product using matrix-assisted laser desorption mass spectrometry indicates that one molecule of chlorambucil cross-links two subunits of the homodimeric protein. A combination of enzymic proteolysis, high performance liquid chromatography, and mass spectrometry reveals that chlorambucil alkylation occurs at cysteine 47 of one subunit and cysteine 101 of the second subunit. This result supports the idea that conformational changes occur in glutathione-depleted pi GST, which allow the bifunctional tether of chlorambucil to cross-link the two subunits of the protein.

Affinity Labels↗
PubMed1996

Characterization of intermediates in the oxidation of zinc fingers in human immunodeficiency virus type 1 nucleocapsid protein P7.

Oxidants targeted toward inactivation of the nucleocapsid zinc finger protein are under development as antiviral agents, especially for use against human immunodeficiency virus. In the present study, electrospray ionization-mass spectrometry is used to follow in situ the progress of the reactions of 2,2'-dithiodipyridine and disulfiram with recombinant nucleocapsid protein p7 (Ncp7) from human immunodeficiency virus-1 at pH 7.4. Both reagents react with the two zinc fingers in the protein, resulting in the ejection of two zinc ions and the formation of oxidized apo-Ncp7 with three intramolecular disulfide bonds. The ejection of zinc by 2,2'-dithiodipyridine occurs in two steps. Alkylation of unreacted cysteine residues with N-ethylmaleimide after a 2-min reaction with 2,2'-dithiodipyridine reveals that the carboxyl-terminal zinc finger is disrupted first. Cys-49, Cys-36, and, to a lesser extent, Cys-39 are all shown to be target residues for initial electrophilic attack. In the reaction of disulfiram with Ncp7, ejection of the two zinc ions also occurs in two steps; however, the fully oxidized apo-Ncp7 is formed more rapidly. Thus, after a 40-min reaction, 45% of native Ncp7 is oxidized by 2,2'-dithiodipyridine, whereas 75% is oxidized by disulfiram.

2,2'-Dipyridyl↗
PubMed1995

Specific disulfide formation in the oxidation of HIV-1 zinc finger protein nucleocapsid p7.

In vitro oxidation of the HIV-1 nucleocapsid protein p7 by the C-nitroso compound 3-nitrosobenzamide (NOBA) has been investigated. When reconstituted p7 was incubated with NOBA, three disulfide bonds were formed per molecule of p7, Cys 15-Cys 18, Cys 28-Cys 36, and Cys 39-Cys 49. These were identified using the proteolytic enzyme endoproteinase Lys-C and mass spectrometry. When the denatured protein (Apo-p7) was incubated with NOBA, a more random pattern of multiple S-S linkages was found. Oxidation of reconstituted p7 also occurred on treatment with cupric ions (Cu2+), and the same three major disulfide bonds were formed as in the reaction with NOBA. These results suggest the interpretation that the oxidation reaction occurs at the zinc-binding centers while zinc cations are still bound and that the two zinc fingers are not identical in their chemical properties. This latter point is consistent with the independent biological roles reported previously for the two fingers in the viral infection cycle.

Amino Acid Sequence↗
PubMed1994

High-performance liquid chromatographic study of the regulation of phospholipid metabolism in cultured adrenocortical cells.

A rapid high-performance liquid chromatographic (HPLC) method for the separation of phospholipids was developed for minute samples of total lipids (ca. 200 micrograms). The method was applied to the study of the phospholipid metabolism in adrenocortical cell cultures. A complete separation of the different cellular phospholipid classes was achieved in 40 min. Good resolution of the phospholipid peaks was obtained, which allowed the collection of each individual class of phospholipids for further analysis of radioactivity and fatty acid composition by gas chromatography. When cells were incubated with [U-14C]glycerol or [U-14C]palmitate the bulk of the radioactivity was found in cellular phosphatidylcholines. Exogenous phospholipids were incorporated into cellular lipids to a large extent, however without an increase in the cellular phospholipid content. 12-O-Tetradecanoyl-phorbol-13-acetate induced a 20% increase in the polyunsaturated fatty acid content of the cellular phosphatidylethanolamines, but no change was detected in the cellular phosphatidylcholines. The developed method is well-suited to the study of the phospholipid metabolism in adrenocortical cells where the phospholipid metabolism is closely linked to the specialized functions of the cells.

Adrenal Cortex↗
PubMed1993

Metabolism of Linoleic Acid or Mevalonate and 6-Pentyl-alpha-Pyrone Biosynthesis by Trichoderma Species.

The understanding of the biosynthetic pathway of 6-pentyl-alpha-pyrone in Trichoderma species was achieved by using labelled linoleic acid or mevalonate as a tracer. Incubation of growing cultures of Trichoderma harzianum and T. viride with [U-C]linoleic acid or [5-C]sodium mevalonate revealed that both fungal strains were able to incorporate these labelled compounds (50 and 15%, respectively). Most intracellular radioactivity was found in the neutral lipid fraction. At the initial time of incubation, the radioactivity from [C]linoleic acid was incorporated into 6-pentyl-alpha-pyrone more rapidly than that from [C]mevalonate. No radioactivity incorporation was detected in 6-pentyl-alpha-pyrone when fungal cultures were incubated with [1-C]linoleic acid. These results suggested that beta-oxidation of linoleic acid was a probable main step in the biosynthetic pathway of 6-pentyl-alpha-pyrone in Trichoderma species.

Journal Article↗
PubMed1992

Quantitative separation of Trichoderma lipid classes on a bonded phase column.

Bond Elut aminopropyl columns were used to purify the different lipid classes of Trichoderma harzianum and Trichoderma viride. This methodology permitted good separation of the fungal lipid classes in less time than traditional techniques. The incorporation of [1 (14)C]linoleic acid into neutral lipids, free fatty acids and phospholipids was quantified for both strains. The fatty acid profile of the different lipid classes of these fungal strains was determined as a function of culture time.

Chromatography↗
PubMed1991

Aldosterone biosynthesis induced by ACTH and angiotensin II in newborn rat adrenocortical cells transfected by c-EJ-Ha-ras oncogene.

Adrenocortical cells were obtained by fractionated trypsination of newborn rat adrenal glands and transfected with a plasmid containing the EJ/T24-Ha-ras oncogene. Isolation of adhesive cells led to a proliferative cell line with an overexpression of 21 kDa ras protein. These cells incubated with corticosterone or deoxycorticosterone as the precursor produced a high level of 18-hydroxycorticosterone and aldosterone as identified by gas chromatography- mass spectrometry. ACTH and angiotensin II increased the basal production of aldosterone nineteen-fold and six-fold respectively. Under ACTH stimulation the ratio between aldosterone and 18-hydroxycorticosterone production was 1:3. The transformation of corticosterone under angiotensin II stimulation yielded up to 41% of 18-hydroxycorticosterone (4.7 micrograms/mg of cell protein per 24h) and 4.4% of aldosterone (0.5 microgram/mg of cell protein per 24h) in a low potassium concentration medium (6 mmol/l). To our knowledge this is the first report of continuous proliferative adrenocortical cells producing aldosterone.

18-Hydroxycorticosterone↗