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161.
162.
Pearson SJ Wharton S Watson AJ Begum G Butt A Glynn N Williams DM Shibata T Santibáñez-Koref MF Margison GP 《Nucleic acids research》2006,34(8):2347-2354
Toxic and mutagenic O6-alkylguanine adducts in DNA are repaired by O6-alkylguanine-DNA alkyltransferases (MGMT) by transfer of the alkyl group to a cysteine residue in the active site. Comparisons in silico of prokaryotes and lower eukaryotes reveal the presence of a group of proteins [alkyltransferase-like (ATL) proteins] showing amino acid sequence similarity to MGMT, but where the cysteine at the putative active site is replaced by tryptophan. To examine whether ATL proteins play a role in the biological effects of alkylating agents, we inactivated the gene, referred to as atl1+, in Schizosaccharomyces pombe, an organism that does not possess a functional MGMT homologue. The mutants are substantially more susceptible to the toxic effects of the methylating agents, N-methyl-N-nitrosourea, N-methyl-N′nitro-N-nitrosoguanidine and methyl methanesulfonate and longer chain alkylating agents including N-ethyl-N-nitrosourea, ethyl methanesulfonate, N-propyl-N-nitrosourea and N-butyl-N-nitrosourea. Purified Atl1 protein does not transfer methyl groups from O6-methylguanine in [3H]-methylated DNA but reversibly inhibits methyl transfer by human MGMT. Atl1 binds to short single-stranded oligonucleotides containing O6-methyl, -benzyl, -4-bromothenyl or -hydroxyethyl-guanine but does not remove the alkyl group or base and does not cleave the oligonucleotide in the region of the lesion. This suggests that Atl1 acts by binding to O6-alkylguanine lesions and signalling them for processing by other DNA repair pathways. This is the first report describing an activity that protects S.pombe against the toxic effects of O6-alkylguanine adducts and the biological function of a family of proteins that is widely found in prokaryotes and lower eukaryotes. 相似文献
163.
Phosphorylation of tau at Ser214 mediates its interaction with 14-3-3 protein: implications for the mechanism of tau aggregation 总被引:1,自引:0,他引:1
Golam Sadik Toshihisa Tanaka Kiyoko Kato Hidenaga Yamamori Begum Nurun Nessa Takashi Morihara Masatoshi Takeda 《Journal of neurochemistry》2009,108(1):33-43
The microtubule associated protein tau is a major component of neurofibrillary tangles in Alzheimer disease brain, however the neuropathological processes behind the formation of neurofibrillary tangles are still unclear. Previously, 14-3-3 proteins were reported to bind with tau. 14-3-3 Proteins usually bind their targets through specific serine/threonine –phosphorylated motifs. Therefore, the interaction of tau with 14-3-3 mediated by phosphorylation was investigated. In this study, we show that the phosphorylation of tau by either protein kinase A (PKA) or protein kinase B (PKB) enhances the binding of tau with 14-3-3 in vitro . The affinity between tau and 14-3-3 is increased 12- to 14-fold by phosphorylation as determined by real time surface plasmon resonance studies. Mutational analyses revealed that Ser214 is critical for the phosphorylation-mediated interaction of tau with 14-3-3. Finally, in vitro aggregation assays demonstrated that phosphorylation by PKA/PKB inhibits the formation of aggregates/filaments of tau induced by 14-3-3. As the phosphorylation at Ser214 is up-regulated in fetal brain, tau's interaction with 14-3-3 may have a significant role in the organization of the microtubule cytoskeleton in development. Also as the phosphorylation at Ser214 is up-regulated in Alzheimer's disease brain, tau's interaction with 14-3-3 might be involved in the pathology of this disease. 相似文献
164.
Chandanapurath Shiny Nagampalli S.A. Krushna Bairavasundaram Archana Begum Farzana Rangarajan B. Narayanan 《Microbiology and immunology》2009,53(12):685-693
Wolbachia surface protein (WSP), which is the most abundantly expressed protein of Wolbachia from the human filarial parasite Brugia malayi, was chosen for the present study. B‐cell epitope prediction of the WSP protein sequence indicates a high antigenicity, surface probability and hydrophilicity by DNA STAR software analysis. ProPred analysis suggests the presence of HLA class II binding regions in the WSP protein that contribute to T‐cell responses and isotype reactivity. In order to validate these findings, the gene coding for endosymbiont WSP was PCR‐amplified from the genomic DNA of the human filarial parasite Brugia malayi and cloned in T‐7 expression vector pRSET‐A. Western blot and ELISA at the total IgG level with recombiant WSP indicated a significantly elevated reactivity in CP compared to MF, EN and NEN individuals. Isotype ELISA also suggested an elevated reactivity in CP patients at the IgG1 level. In contrast, WSP‐specific IgG4 levels were found to be elevated in MF patients compared to CP and EN. Besides this, WSP‐specific IgE levels indicated an elevated reactivity in CP and MF patients compared to normals. Observations from ELISA supported the in silico predictions that indicate the presence of B‐ and T‐cell epitopes. Hence, a combinatorial approach of in silico predictions and wet‐lab studies provides interesting insights into the role of Wolbachia proteins in filarial pathogenesis. 相似文献
165.
Katsumune Takahashi Rumi Shizume Katsumi Uchida Hirofumi Yajima 《Journal of Biorheology》2009,23(1):64-71
Single-walled carbon nanotubes are novel molecular-scale wires having excellent anti-adhesion properties with regard to platelets.
On the other hand, chitosan is a partially de-acetylated derivative of chitin that has a critical role in cell attachment
and growth. The aim of this study was to investigate how carbon nanotubes improve the blood biocompatibility of chitosan film.
We prepared composite films with various concentrations of chitosan/carbon nanotubes (CS/CNTs) (1.3–6.3 wt%). The sample surfaces
were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact
angle measurements. The surface characterization revealed that the surface of the CS/CNTs composite film became more hydrophobic
with increasing amounts of CNTs. Cell attachment tests using bovine aortic endothelial cells (BAECs) indicated that CS/CNTs
composite films retained their cell adhesion ability. The blood compatibility of the CS/CNTs composite films was evaluated
using the blood platelet adhesion and activation tests in vitro. Platelet adhesion results confirmed that platelet adhesion
and the formation of a platelet network were inhibited on composite films with higher concentrations of CNTs (5.1 wt%). Our
experimental results show that the novel composite film containing CS/CNTs possesses two paradoxical characteristics, namely,
good adherence of endothelial cells and minimum adherence and activation of platelets, making this film a promising antithrombogenic
material for use in the biomedical field. 相似文献
166.
167.
Heteromorphisms between sex chromosomes are rarely found in anurans and sex chromosome differentiation is considered to be a set of recent recurrent events in the evolutionary history of this group. This paper describes for the first time heteromorphic sex chromosomes Z and W in the leiuperid genus Physalaemus. They were found in P. ephippifer, a species of the P. cuvieri group, and corresponded to the eighth pair of its karyotype. The W chromosome differed from the Z chromosome by the presence of an additional segment in the short arm, composed of a distal NOR and an adjacent terminal DAPI-positive C-band. The identification of this sex chromosome pair may help in future investigations into the sex determining genes in the genus Physalaemus. 相似文献
168.
169.
Mohammed S. Ameerunisha Begum 《Journal of inorganic biochemistry》2010,104(4):477-270
Iron(III) complexes [Fe(L)2]Cl (1-3), where L is monoanionic N-salicylidene-arginine (sal-argH for 1), hydroxynaphthylidene-arginine (nap-argH for 2) and N-salicylidene-lysine (sal-lysH for 3), were prepared and their DNA binding and photo-induced DNA cleavage activity studied. Complex 3 as its hexafluorophosphate salt [Fe(sal-lysH)2](PF6)·6H2O (3a) was structurally characterized by single crystal X-ray crystallography. The crystals belonged to the triclinic space group P-1. The complex has two tridentate ligands in FeN2O4 coordination geometry with two pendant cationic amine moieties. Complexes 1 and 2 with two pendant cationic guanidinium moieties are the structural models for the antitumor antibiotics netropsin. The complexes are stable and soluble in water. They showed quasi-reversible Fe(III)/Fe(II) redox couple near 0.6 V in H2O-0.1 M KCl. The high-spin 3d5-iron(III) complexes with μeff value of ∼5.9 μB displayed ligand-to-metal charge transfer electronic band near 500 nm in Tris-HCl buffer. The complexes show binding to Calf Thymus (CT) DNA. Complex 2 showed better binding propensity to the synthetic oligomer poly(dA)·poly(dT) than to CT-DNA or poly(dG)·poly(dC). All the complexes displayed chemical nuclease activity in the presence of 3-mercaptopropionic acid as a reducing agent and cleaved supercoiled pUC19 DNA to its nicked circular form. They exhibited photo-induced DNA cleavage activity in UV-A light and visible light via a mechanistic pathway that involves the formation of reactive hydroxyl radical species. 相似文献
170.
The presence and distribution in Argentina of the invasive snail species Theba pisana is presented on the basis of a survey carried out in 10 beach resorts along the Atlantic coast of Buenos Aires Province.
Additionally, complementary information and complete revision of material of other exotic terrestrial gastropods housed in
museum collections was carried out, reporting herein seven new species for Argentina (Otala punctata, Hawaiia minuscula, Paralaoma servilis, Opeas goodalli, Vallonia pulchella, Vertigo ovata and Pupisoma dioscoricola), one for Colombia (Subulina octona), and two for Peru (S. octona and P. dioscoricola). At present, 42 introduced species of terrestrial gastropods have been recorded in nine countries of South America (Argentina,
Bolivia, Brazil, Chile, Colombia, Paraguay, Peru, Uruguay and Venezuela). The most likely pathways for introduction of terrestrial
gastropods, at least in Argentina, are horticultural development and urban and suburban transformation of original natural
habitats. 相似文献