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51.
The first enzyme of the lysine-biosynthesis pathway, dihydrodipicolinate synthase (DHDPS; EC 4.2.1.52) has been purified and
characterized inNicotiana sylvestris Speggazini et Comes. A purification scheme was developed for the native DHDPS that subsequently led to the purification to
homogeneity of its subunits using two-dimensional gel electrophoresis. Subsequent elution of the purified polypeptide has
opened the way for the production of rabbit polyclonal anti-DHDPS sera. The molecular weight of the enzyme was determined
to be 164000 daltons (Da) by an electrophoretic method. By labeling with [14C]pyruvate, the enzyme was shown to be composed of four identical subunits of 38500 Da. Pyruvate acts as a stabilizing agent
and contributes to the preservation of the tetrameric structure of the enzyme. The enzyme ofN. sylvestris is strongly inhibited by lysine with anI
0.5
of 15 μM; S-(2-aminoethyl)L-cysteine and γ-hydroxylysine, two lysine analogs, were found to be only weak inhibitors. An analog of pyruvate, 2-oxobutyrate,
competitively inhibited the enzyme and was found to act at the level of the pyruvate-binding site. Dihydrodipicolinate synthase
was localized in the chloroplast and identified as a soluble stromal enzyme by enzymatic and immunological methods. Its properties
are compared with those known for other plant and bacterial DHDPS enzymes. 相似文献
52.
C Navarre M Ghislain S Leterme C Ferroud J P Dufour A Goffeau 《The Journal of biological chemistry》1992,267(9):6425-6428
The purified plasma membrane H(+)-ATPase of Schizosaccharomyces pombe and Saccharomyces cerevisiae display, in addition to the catalytic subunit of 100 kDa, a highly mobile component, soluble in chloroform/methanol. Chloroform/methanol extraction of S. cerevisiae plasma membranes led to isolation of a low molecular weight proteolipid identical to that present in purified H(+)-ATPase. NH2-terminal amino acid sequencing revealed a 38-residue polypeptide with a calculated molecular mass of 4250 Da. The polypeptide lacks the first two NH2-terminal amino acids as compared with the deduced sequence of the PMP1 gene (for plasma membrane proteolipid) isolated by hybridization with an oligonucleotide probe corresponding to an internal amino acid sequence of the proteolipid. The polypeptide is predicted to contain an NH2-terminal transmembrane segment followed by a very basic hydrophilic domain. 相似文献
53.
Molecular phylogenetic analyses indicate paraphyly of the genus Hybomys (Rodentia: Muridae): Taxonomic implications
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Alain Didier Missoup Ghislain D. Yemchui Christiane Denys Violaine Nicolas 《Journal of Zoological Systematics and Evolutionary Research》2018,56(3):444-452
Widely distributed in Guineo‐Congolian forests, the genus Hybomys is represented by two species complexes (univittatus and trivirgatus), each restricted to one distinct forest block. In the last revision, these two species complexes were considered as distinct subgenera (Hybomys and Typomys). Previous morphological and karyological studies identified an important divergence between these two subgenera and raised the question of their taxonomic status (subgenus or genus). The number of species within this genus is also a matter of discussion: nine forms were described but only six (H. badius, H. basilii, H. lunaris, H. planifrons, H. trivirgatus, and H. univitttatus) are currently recognized as distinct species, the three others (H. pearcei, H. eisentrauti, and H. rufocanus) being considered as synonyms. The monophyly of the genus and its species have never been previously investigated with DNA sequence data. In this study, we combined mitochondrial and nuclear data (for a total of 3,264 nucleotide characters) to test the monophyly of Hybomys and to assess the specific status of H. eisentrauti and H. rufocanus. Our results highlight the paraphyly of the genus: members of the H. univittatus species complex appeared closely related to the genera Stochomys and Dephomys; representatives of H. trivirgatus are the sister clade of the node grouping Stochomys, Dephomys and member of the H. univittatus species complex. Combined with previous morphological findings, our results suggest that Typomys and Hybomys should be considered as two distinct genera. Based on tree topology and genetic distances, we propose to consider H. rufocanus as a valid species, distinct from H. univittaus, and to consider H. badius and H. eisentrauti as junior synonyms of H. rufocanus. 相似文献
54.
A dinucleotide mutation in dihydrodipicolinate synthase of Nicotiana sylvestris leads to lysine overproduction 总被引:4,自引:0,他引:4
Marc Ghislain Valerie Frankard Michel Jacobs 《The Plant journal : for cell and molecular biology》1995,8(5):733-743
By applying a mutagenesis/selection procedure to obtain resistance to a lysine analog, S-(2-aminoethyl)l -cysteine (AEC), a lysine overproducing mutant in Nicotiana sylvestris was isolated. Amino acid analyses performed throughout plant development and of different organs of the N. sylvestris RAEC-1 mutant, revealed a developmental-dependent accumulation of free lysine. Lysine biosynthesis in the RAEC-1 mutant was enhanced due to a lysine feedback-desensitized dihydrodipicolinate synthase (DHDPS). Several molecular approaches were undertaken to identify the nucleotide change in the dhdps-r1 gene, the mutated gene coding for the lysine-desensitized enzyme. The enzyme was purified from wild-type plants for amino end microsequencing and 10 amino acids were identified. Using dicotyledon dhdps probes, a genomic fragment was cloned from an enriched library of DNA from the homozygote RAEC-1 mutant plant. A dhdps cDNA, putatively full-length, was isolated from a tobacco cDNA library. Nucleotide sequence analyses confirmed the presence of the previously identified amino end preceded by a chloroplast transit peptide sequence. Nucleotide sequence comparisons, enzymatic and immunological analyses revealed that the tobacco cDNA corresponds to a normal type of DHDPS, lysine feedback-regulated, and the genomic fragment to the mutated DHDPS, insensitive to lysine inhibition. Functional complementation of a DHDPS-deficient Escherichia coli strain was used as an expression system. Reconstruction between the cDNA and genomic fragment led to the production of a cDNA producing an insensitive form of DHDPS. Amino acid sequence comparisons pointed out, at position 104 from the first amino acid of the mature protein, the substitution of Asn to lleu which corresponds to a dinucleotide mutation. This change is unique to the dhdps-r1 gene when compared with the wild-type sequence. The identification of the nucleotide and amino acid change of the lysine-desensitized DHDPS from RAEC-1 plant opens new perspectives for the improvement of the nutritional value of crops and possibly to develop a new plant selectable marker. 相似文献
55.
Alban de Kerchove d'Exaerde Pierre Morsomme Denise Sempoux-Thinès Philip Supply ré Goffeau & Michel Ghislain 《Molecular microbiology》1997,25(2):261-273
The plasma membrane H+ -ATPase from the fission yeast Schizosaccharomyces pombe does not support growth of H+ -ATPase-depleted cells of the budding yeast Saccharomyces cerevisiae , even after deletion of the enzyme's carboxy terminus. Functional chimerical H+ -ATPase proteins in which appropriate regions of the S. pombe enzyme were replaced with their S. cerevisiae counterparts were generated by in vivo gene recombination. Site-directed mutagenesis of the H+ -ATPase chimeras showed that a single amino acid replacement, tyrosine residue 596 by alanine, resulted in functional expression of the S. pombe H+ -ATPase. The reverse Ala-598 →Tyr substitution was introduced into the S. cerevisiae enzyme to better understand the role of this alanine residue. However, no obvious effect on ATPase activity could be detected. The S. cerevisiae cells expressing the S. pombe H+ -ATPase substituted with alanine were enlarged and grew more slowly than wild-type cells. ATPase activity showed a more alkaline pH optimum, lower K m values for MgATP and decreased V max compared with wild-type S. cerevisiae activity. None of these kinetic parameters was found to be modified in glucose-starved cells, indicating that the S. pombe H+ -ATPase remained fully active. Interestingly, regulation of ATPase activity by glucose was restored to a chimera in which the S. cerevisiae sequence spans most of the catalytic site. 相似文献
56.
Novel transport ATPases in yeast 总被引:1,自引:0,他引:1
A Goffeau M Ghislain C Navarre B Purnelle P Supply 《Biochimica et biophysica acta》1990,1018(2-3):200-202
57.
Marike Alferink Janine de Zeeuw Ghislain Sopoh Chantal Agossadou Karibu M. Abass Richard O. Phillips Susanne Loth Emma Jutten Yves T. Barogui Roy E. Stewart Tjip S. van der Werf Ymkje Stienstra Adelita V. Ranchor 《PloS one》2015,10(6)
Buruli ulcer (BU) is a necrotizing skin disease caused by Mycobacterium ulcerans. People living in remote areas in tropical Sub Saharan Africa are mostly affected. Wound care is an important component of BU management; this often needs to be extended for months after the initial antibiotic treatment. BU is reported in the literature as being painless, however clinical observations revealed that some patients experienced pain during wound care. This was the first study on pain intensity during and after wound care in BU patients and factors associated with pain. In Ghana and Benin, 52 BU patients above 5 years of age and their relatives were included between December 2012 and May 2014. Information on pain intensity during and after wound care was obtained during two consecutive weeks using the Wong-Baker Pain Scale. Median pain intensity during wound care was in the lower range (Mdn = 2, CV = 1), but severe pain (score > 6) was reported in nearly 30% of the patients. Nevertheless, only one patient received pain medication. Pain declined over time to low scores 2 hours after treatment. Factors associated with higher self-reported pain scores were; male gender, fear prior to treatment, pain during the night prior to treatment, and pain caused by cleaning the wound. The general idea that BU is painless is incorrect for the wound care procedure. This procedural pain deserves attention and appropriate intervention. 相似文献
58.
Asner GP Mascaro J Muller-Landau HC Vieilledent G Vaudry R Rasamoelina M Hall JS van Breugel M 《Oecologia》2012,168(4):1147-1160
Airborne light detection and ranging (LiDAR) is fast turning the corner from demonstration technology to a key tool for assessing
carbon stocks in tropical forests. With its ability to penetrate tropical forest canopies and detect three-dimensional forest
structure, LiDAR may prove to be a major component of international strategies to measure and account for carbon emissions
from and uptake by tropical forests. To date, however, basic ecological information such as height–diameter allometry and
stand-level wood density have not been mechanistically incorporated into methods for mapping forest carbon at regional and
global scales. A better incorporation of these structural patterns in forests may reduce the considerable time needed to calibrate
airborne data with ground-based forest inventory plots, which presently necessitate exhaustive measurements of tree diameters
and heights, as well as tree identifications for wood density estimation. Here, we develop a new approach that can facilitate
rapid LiDAR calibration with minimal field data. Throughout four tropical regions (Panama, Peru, Madagascar, and Hawaii),
we were able to predict aboveground carbon density estimated in field inventory plots using a single universal LiDAR model
(r
2
= 0.80, RMSE = 27.6 Mg C ha−1). This model is comparable in predictive power to locally calibrated models, but relies on limited inputs of basal area and
wood density information for a given region, rather than on traditional plot inventories. With this approach, we propose to
radically decrease the time required to calibrate airborne LiDAR data and thus increase the output of high-resolution carbon
maps, supporting tropical forest conservation and climate mitigation policy. 相似文献
59.
Telomere tethering at the nuclear periphery is essential for efficient DNA double strand break repair in subtelomeric region
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Therizols P Fairhead C Cabal GG Genovesio A Olivo-Marin JC Dujon B Fabre E 《The Journal of cell biology》2006,172(2):189-199
In the yeast Saccharomyces cerevisiae that lacks lamins, the nuclear pore complex (NPC) has been proposed to serve a role in chromatin organization. Here, using fluorescence microscopy in living cells, we show that nuclear pore proteins of the Nup84 core complex, Nup84p, Nup145Cp, Nup120p, and Nup133p, serve to anchor telomere XI-L at the nuclear periphery. The integrity of this complex is shown to be required for repression of a URA3 gene inserted in the subtelomeric region of this chromosome end. Furthermore, altering the integrity of this complex decreases the efficiency of repair of a DNA double-strand break (DSB) only when it is generated in the subtelomeric region, even though the repair machinery is functional. These effects are specific to the Nup84 complex. Our observations thus confirm and extend the role played by the NPC, through the Nup84 complex, in the functional organization of chromatin. They also indicate that anchoring of telomeres is essential for efficient repair of DSBs occurring therein and is important for preserving genome integrity. 相似文献
60.