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951.
Davis AJ Perugini MA Smith BJ Stewart JD Ilg T Hodder AN Handman E 《The Journal of biological chemistry》2004,279(13):12462-12468
Leishmania parasites synthesize a range of mannose-containing glycoconjugates thought to be essential for virulence in the mammalian host and sandfly vector. A prerequisite for the synthesis of these molecules is the availability of the activated mannose donor, GDP-Man, the product of the catalysis of mannose-1-phosphate and GTP by GDP-mannose pyrophosphorylase (GDP-MP). In contrast to the lethal phenotype in fungi, the deletion of the gene in Leishmania mexicana did not affect parasite viability but led to a total loss of virulence, making GDP-MP an ideal target for anti-Leishmania drug development. We show by immunofluorescence and subcellular fractionation that GDP-MP is a cytoplasmic protein, and we describe a colorimetric activity assay suitable for the high throughput screening of small molecule inhibitors. We expressed recombinant GDP-MP as a fusion with maltose-binding protein and separated the enzyme from maltose-binding protein by thrombin cleavage, ion-exchange, and size exclusion chromatography. Size exclusion chromatography and analytical ultracentrifugation studies demonstrate that GDP-MP self-associates to form an enzymatically active and stable hexamer. However, sedimentation studies show that the GDP-MP hexamer dissociates to trimers and monomers in a time-dependent manner, at low protein concentrations, at low ionic strength, and at alkaline pH. Circular dichroism spectroscopy reveals that GDP-MP is comprised of mixed alpha/beta structure, similar to its closest related homologue, N-acetyl-glucoseamine-1-phosphate uridyltransferase (Glmu) from Streptococcus pneumoniae. Our studies provide insight into the structure of a novel target for the development of anti-Leishmania drugs. 相似文献
952.
953.
Frank Qian Temidayo Ogundiran Ningqi Hou Paul Ndom Antony Gakwaya Johashaphat Jombwe Imran Morhason-Bello Clement Adebamowo Adeyinka Ademola Oladosu Ojengbede Olufunmilayo I. Olopade Dezheng Huo 《PloS one》2014,9(9)
Background
Alcohol drinking is linked to the development of breast cancer. However, there is little knowledge about the impact of alcohol consumption on breast cancer risk among African women.Methods
We conducted a case-control study among 2,138 women with invasive breast cancer and 2,589 controls in Nigeria, Cameroon, and Uganda from 1998 to 2013. A structured questionnaire was used to collect information on alcohol consumption, defined as consuming alcoholic beverages at least once a week for six months or more. Logistic regression was used to estimate adjusted odds ratio (aOR) and 95% confidence interval (CI).Results
Among healthy controls, the overall alcohol consumption prevalence was 10.4%, and the prevalence in Nigeria, Cameroon, and Uganda were 5.0%, 34.6%, and 50.0%, respectively. Cases were more likely to have consumed alcohol (aOR = 1.62, 95% CI: 1.33–1.97). Both past (aOR = 1.54; 95% CI: 1.19–2.00) and current drinking (aOR = 1.71; 95% CI: 1.30–2.23) were associated with breast cancer risk. A dose-response relationship was observed for duration of alcohol drinking (P-trend <0.001), with 10-year increase of drinking associated with a 54% increased risk (95% CI: 1.29–1.84).Conclusion
We found a positive relationship between alcohol consumption and breast cancer risk, suggesting that this modifiable risk factor should be addressed in breast cancer prevention programs in Africa. 相似文献954.
Role of the Schizosaccharomyces pombe F-Box DNA helicase in processing recombination intermediates 下载免费PDF全文
Morishita T Furukawa F Sakaguchi C Toda T Carr AM Iwasaki H Shinagawa H 《Molecular and cellular biology》2005,25(18):8074-8083
In an effort to identify novel genes involved in recombination repair, we isolated fission yeast Schizosaccharomyces pombe mutants sensitive to methyl methanesulfonate (MMS) and a synthetic lethal with rad2. A gene that complements such mutations was isolated from the S. pombe genomic library, and subsequent analysis identified it as the fbh1 gene encoding the F-box DNA helicase, which is conserved in mammals but not conserved in Saccharomyces cerevisiae. An fbh1 deletion mutant is moderately sensitive to UV, MMS, and gamma rays. The rhp51 (RAD51 ortholog) mutation is epistatic to fbh1. fbh1 is essential for viability in stationary-phase cells and in the absence of either Srs2 or Rqh1 DNA helicase. In each case, lethality is suppressed by deletion of the recombination gene rhp57. These results suggested that fbh1 acts downstream of rhp51 and rhp57. Following UV irradiation or entry into the stationary phase, nuclear chromosomal domains of the fbh1Delta mutant shrank, and accumulation of some recombination intermediates was suggested by pulsed-field gel electrophoresis. Focus formation of Fbh1 protein was induced by treatment that damages DNA. Thus, the F-box DNA helicase appears to process toxic recombination intermediates, the formation of which is dependent on the function of Rhp51. 相似文献
955.
Parker AR O'Meally RN Sahin F Su GH Racke FK Nelson WG DeWeese TL Eshleman JR 《The Journal of biological chemistry》2003,278(48):47937-47945
Oxidative DNA damage can generate a variety of cytotoxic DNA lesions such as 8-oxoguanine (8-oxoG), which is one of the most mutagenic bases formed from oxidation of genomic DNA because 8-oxoG can readily mispair with either cytosine or adenine. If unrepaired, further replication of A.8-oxoG mispairs results in C:G to A:T transversions, a form of genomic instability. We reported previously that repair of A.8-oxoG mispairs was defective and that 8-oxoG levels were elevated in several microsatellite stable human colorectal cancer cell lines lacking MutY mutations (human MutY homolog gene, hmyh, MYH MutY homolog protein). In this report, we provide biochemical evidence that the defective repair of A.8-oxoG may be due, at least in part, to defective phosphorylation of the MutY protein in these cell lines. In MutY-defective cell extracts, but not extracts with functional MutY, A.8-oxoG repair was increased by incubation with protein kinases A and C (PKA and PKC) and caesin kinase II. Treatment of these defective cells, but not cells with functional MutY, with phorbol-12-myristate-13-acetate also increased the cellular A.8-oxoG repair activity and decreased the elevated 8-oxoG levels. We show that MutY is serine-phosphorylated in vitro by the action of PKC and in the MutY-defective cells by phorbol-12-myristate-13-acetate but that MutY is already phosphorylated at baseline in proficient cell lines. Finally, using antibody-isolated MutY protein, we show that MutY can be directly phosphorylated by PKC that directly increases the level of MutY catalyzed A.8-oxoG repair. 相似文献
956.
Gopalasamy Reuben Clements Antony J. Lynam David Gaveau Wei Lim Yap Stanislav Lhota Miriam Goosem Susan Laurance William F. Laurance 《PloS one》2014,9(12)
Habitat destruction and overhunting are two major drivers of mammal population declines and extinctions in tropical forests. The construction of roads can be a catalyst for these two threats. In Southeast Asia, the impacts of roads on mammals have not been well-documented at a regional scale. Before evidence-based conservation strategies can be developed to minimize the threat of roads to endangered mammals within this region, we first need to locate where and how roads are contributing to the conversion of their habitats and illegal hunting in each country. We interviewed 36 experts involved in mammal research from seven Southeast Asian countries to identify roads that are contributing the most, in their opinion, to habitat conversion and illegal hunting. Our experts highlighted 16 existing and eight planned roads - these potentially threaten 21% of the 117 endangered terrestrial mammals in those countries. Apart from gathering qualitative evidence from the literature to assess their claims, we demonstrate how species-distribution models, satellite imagery and animal-sign surveys can be used to provide quantitative evidence of roads causing impacts by (1) cutting through habitats where endangered mammals are likely to occur, (2) intensifying forest conversion, and (3) contributing to illegal hunting and wildlife trade. To our knowledge, ours is the first study to identify specific roads threatening endangered mammals in Southeast Asia. Further through highlighting the impacts of roads, we propose 10 measures to limit road impacts in the region. 相似文献
957.
Satinder K Singh Stephen P Miller Antony Dean Leonard J Banaszak David C LaPorte 《The Journal of biological chemistry》2002,277(9):7567-7573
In Escherichia coli, the homodimeric Krebs cycle enzyme isocitrate dehydrogenase (EcIDH) is regulated by reversible phosphorylation of a sequestered active site serine. The phosphorylation cycle is catalyzed by a bifunctional protein, IDH kinase/phosphatase (IDH-K/P). To better understand the nature of the interaction between EcIDH and IDH-K/P, we have examined the ability of an IDH homologue from Bacillus subtilis (BsIDH) to serve as a substrate for the kinase and phosphatase activities. BsIDH exhibits extensive sequence and structural similarities with EcIDH, particularly around the phosphorylated serine. Our previous crystallographic analysis revealed that the active site architecture of these two proteins is almost completely conserved. We now expand the comparison to include a number of biochemical properties. Both IDHs display nearly equivalent steady-state kinetic parameters for the dehydrogenase reaction. Both proteins are also phosphorylated by IDH-K/P in the same ratio (1 mole of phosphate per mole of monomer), and this stoichiometric phosphorylation correlates with an equivalent inhibition of IDH activity. Furthermore, tandem electrospray mass spectrometry demonstrates that BsIDH, like EcIDH, is phosphorylated on the corresponding active site serine residue (Ser-104). Despite the high degree of sequence, functional, and structural congruence between these two proteins, BsIDH is surprisingly a much poorer substrate of IDH-K/P than is EcIDH, with Michaelis constants for the kinase and phosphatase activities elevated by 60- and 3,450-fold, respectively. These drastically disparate values might result from restricted access to the active site cavity and/or from the lack of a potential docking site for IDH-K/P. 相似文献
958.
959.
Antibodies raised against deoxyadenylate and deoxycytidylate were found to react with double stranded DNA as assessed by highly sensitive avidin-biotin microELISA. The binding was specific as it was completely inhibited by the homologous hapten. The antibodies did not react with tRNA and rRNA. These antibodies were also shown to react with supercoiled and relaxed forms of pBR322 DNA as demonstrated by gel retardation assay. 相似文献
960.
Gary A. Flynn Ann L. Akeson Ram Dharanipragada Michael J. Genin J. Antony Malikayil Richard Pottorf Jeffery S. Sabol Herman Schreuder Ron Tomlinson Phil Waid Ron Barrett Jeff Jacobs Steve Yanofsky 《International journal of peptide research and therapeutics》1998,5(2-3):93-100
Summary A collection of complementary peptide caricatures that closely mimic low-energy (presumably highly populated) conformations
of amino acids of interest would constitute a valuable tool set to study the interactions of small peptide ligands with their
biological targets. Our general strategy for the design, synthesis and application of peptidomimetics is presented. An illustration
of how structural information from mimetics combined with cutting edge biophysical data can be used to derive a model for
the bound conformation of an 11-mer peptide antagonist with the IL-1 receptor is given. 相似文献