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51.
Kathy R. Chaurasiya Clarissa Ruslie Michelle C. Silva Lukas Voortman Philip Nevin Samer Lone Penny J. Beuning Mark C. Williams 《Nucleic acids research》2013,41(19):8959-8968
Replication by Escherichia coli DNA polymerase III is disrupted on encountering DNA damage. Consequently, specialized Y-family DNA polymerases are used to bypass DNA damage. The protein UmuD is extensively involved in modulating cellular responses to DNA damage and may play a role in DNA polymerase exchange for damage tolerance. In the absence of DNA, UmuD interacts with the α subunit of DNA polymerase III at two distinct binding sites, one of which is adjacent to the single-stranded DNA-binding site of α. Here, we use single molecule DNA stretching experiments to demonstrate that UmuD specifically inhibits binding of α to ssDNA. We predict using molecular modeling that UmuD residues D91 and G92 are involved in this interaction and demonstrate that mutation of these residues disrupts the interaction. Our results suggest that competition between UmuD and ssDNA for α binding is a new mechanism for polymerase exchange. 相似文献
52.
Nadia M. S. Arafa Mona Abdel-Rahman Manal F. El-khadragy Rami B. Kassab 《Neurochemical research》2013,38(1):174-185
The neuroprotective effect of Nigella sativa (NS) on amino acid neurotransmitters alteration in pentylenetetrazole (PTZ) and ciprofloxacin (CFX) treated rats in different brain regions was examined. The oral administration of NS induced an elevation in aspartate and glutamate contents, whereas the levels of GABA and glycine were decreased. Furthermore, the treated groups with PTZ and CFX caused a decrease in aspartate, glutamate and total antioxidant capacity levels, while the concentrations of GABA and glycine were increased after 14 days. Moreover, the pre- and post-treatment with NS in PTZ and CFX treated rats return the levels of these parameters near control values. So, it could be concluded that the treatment with CFX induced imbalance between the excitatory and the inhibitory amino acids which may lead to the initiation of epileptic seizures and the treatment with NS was found to ameliorate these neurological defects which reflect its potent antiepileptic activity. 相似文献
53.
In Egypt, β-thalassemia is the most common hereditary hemolytic anemia. Cardiac dysfunction, secondary to iron overload with formation of oxygen free radicals, is the most common cause of death in β-thalassemia patients. This study was designed to determine whether the allelic genotype of apolipoprotein E (Apo E), which exhibits antioxidant properties, could represent a genetic risk factor for the development of left ventricular (LV) dysfunction in β-thalassemia major. Fifty Egyptian β-thalassemia major patients were subjected to echocardiography to assess LV function. Apo E genotyping by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) was done for all patients in addition to 50 age and sex matched healthy control subjects. Patients were classified into three groups. Group I and II were clinically asymptomatic. Group II subjects had evidence of LV dilatation, while Group III patients had clinical and echocardiographic findings of LV failure. Apo E4 allele was significantly higher among Group II and III than in controls. In conclusion, Apo E4 allele can be considered as a genetic risk factor for LV dysfunctions in β-thalassemic patients. It could be used as predictive indicator for additional risk of LV failure, particularly in asymptomatic patients with LV dilatation, requiring a closer follow-up, to prevent further disease progression. 相似文献
54.
Qilu Ye Yedan Feng Yanxia Yin Frédérick Faucher Mark A. Currie Mona N. Rahman Jin Jin Shanze Li Qun Wei Zongchao Jia 《Cellular signalling》2013,25(12):2661-2667
Calcineurin is the only known calmodulin (CaM) activated protein phosphatase, which is involved in the regulation of numerous cellular and developmental processes and in calcium-dependent signal transduction. Although commonly assumed that CaM displaces the autoinhibitory domain (AID) blocking substrate access to its active site, the structural basis underlying activation remains elusive. We have created a fused ternary complex (CBA) by covalently linking three polypeptides: CaM, calcineurin regulatory B subunit (CnB) and calcineurin catalytic A subunit (CnA). CBA catalytic activity is comparable to that of fully activated native calcineurin in the presence of CaM. The crystal structure showed virtually no structural change in the active site and no evidence of CaM despite being covalently linked. The asymmetric unit contains four molecules; two parallel CBA pairs are packed in an antiparallel mode and the large cavities in crystal packing near the calcineurin active site would easily accommodate multiple positions of AID-bound CaM. Intriguingly, the conformation of the ordered segment of AID is not altered by CaM; thus, it is the disordered part of AID, which resumes a regular α-helical conformation upon binding to CaM, which is displaced by CaM for activation. We propose that the structural basis of calcineurin activation by CaM is through displacement of the disordered fragment of AID which otherwise impedes active site access. 相似文献
55.
56.
Kurt Kräuchi Christian Cajochen Mona Pache Josef Flammer Anna Wirz‐Justice 《Chronobiology international》2013,30(1-2):475-484
Thermoregulatory processes have long been implicated in the initiation of human sleep. In this paper, we review our own studies conducted over the last decade showing a crucial role for melatonin as a mediator between the thermoregulatory and arousal system in humans. Distal heat loss, via increased skin temperature, seems to be intimately coupled with increased sleepiness and sleep induction. Exogenous melatonin administration during the day when melatonin is essentially absent mimics the endogenous thermophysiological processes occurring in the evening and induces sleepiness. Using a cold thermic challenge test, it was shown that melatonin‐induced sleepiness occurs in parallel with reduction in the thermoregulatory set‐point (threshold); thus, melatonin may act as a circadian modulator of the thermoregulatory set‐point. In addition, an orthostatic challenge can partially block the melatonin‐induced effects, suggesting an important role of the sympathetic nervous system as a link between the thermoregulatory and arousal systems. A topographical analysis of finger skin temperature with infrared thermometry revealed that the most distal parts of the fingers, i.e., fingertips, represent the important skin regions for heat loss regulation, most probably via opening the arteriovenous anastomoses, and this is clearly potentiated by melatonin. Taken together, melatonin is involved in the fine‐tuning of vascular tone in selective vascular beds, as circulating melatonin levels rise and fall throughout the night. Besides the role of melatonin as “nature's soporific”, it can also serve as nature's nocturnal vascular modulator. 相似文献
57.
Benoit Marteyn Samer Sakr Sandrine Farci Mariette Bedhomme Solenne Chardonnet Paulette Decottignies Stéphane D. Lemaire Corinne Cassier-Chauvat Franck Chauvat 《Journal of bacteriology》2013,195(18):4138-4145
In a continuing effort to analyze the selectivity/redundancy of the three glutaredoxin (Grx) enzymes of the model cyanobacterium Synechocystis PCC6803, we have characterized an enzyme system that plays a crucial role in protection against two toxic metal pollutants, mercury and uranium. The present data show that Grx1 (Slr1562 in CyanoBase) selectively interacts with the presumptive mercuric reductase protein (Slr1849). This MerA enzyme plays a crucial role in cell defense against both mercuric and uranyl ions, in catalyzing their NADPH-driven reduction. Like MerA, Grx1 operates in cell protection against both mercury and uranium. The Grx1-MerA interaction requires cysteine 86 (C86) of Grx1 and C78 of MerA, which is critical for its reductase activity. MerA can be inhibited by glutathionylation and subsequently reactivated by Grx1, likely through deglutathionylation. The two Grx1 residues C31, which belongs to the redox active site (CX2C), and C86, which operates in MerA interactions, are both required for reactivation of MerA. These novel findings emphasize the role of glutaredoxins in tolerance to metal stress as well as the evolutionary conservation of the glutathionylation process, so far described mostly for eukaryotes. 相似文献
58.
Aika Yamaguchi Mona Hoppenrath Vera Pospelova Takeo Horiguchi Brian S. Leander 《欧洲藻类学杂志》2013,48(2):98-104
Herdmania litoralis is a heterotrophic, sand-dwelling dinoflagellate with morphological characters that do not provide clear evidence for its systematic position in any existing family of dinoflagellates. Protoperidinium minutum is a heterotrophic, planktonic species that has a typical tabulation for the genus Protoperidinium. In order to infer the phylogenetic positions of these two species more confidently, we characterized the thecal plate patterns and determined small-subunit and large-subunit ribosomal DNA sequences (SSU rDNA and LSU rDNA, respectively) from both species. Intraindividual and intraspecific diversity of SSU and LSU rDNA data were characterized in H. litoralis using a combination of single-cell PCR approaches and analyses of PCR clones derived from multi-cell DNA extractions. The results of the molecular phylogenetic analyses demonstrated a novel, well-supported clade comprising both sand-dwelling species (H. litoralis and Thecadinium dragescoi) and planktonic species (P. minutum). Because the establishment of this clade also demonstrated that P. minutum is not a member of Protoperidinium, we reinstated and emended the genus Archaeperidinium Jörgensen 1912. 相似文献
59.
Lizette Auezova Fadia Najjar Olga Selivanova Elie Hajj Moussa Mona Diab Assaf 《Journal of applied phycology》2013,25(4):1189-1196
The present study aims to investigate the levels of polyphenols and antioxidant activity in one of the most important commercial species of seaweeds in Kamchatka, an edible brown seaweed Saccharina bongardiana. Six extracts of S. bongardiana, acetone, methanol, ethanol, and the respective 70 % aqueous solutions, were assessed for total phenol content in order to determine the most efficient extracting solvent. The total phenol content was measured by the Folin–Ciocalteu method and expressed as phloroglucinol equivalents (PGE). The antioxidant tests used were 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, linoleic acid-β carotene oxidation inhibiting assay, and Fe2+ ion chelating method. Higher phenolic contents were obtained using aqueous organic solvents, as compared to the respective absolute solvents; 70 % acetone was found to be the most efficient solvent (1.039 mg PGE 100 mg?1 dry algal powder). High significant correlations were noted between total phenol content and the tested antioxidant activities; so the aqueous organic extracts exhibited the highest antioxidant activities versus DPPH radicals (EC50 values of 0.6–1.1 mg dry weight (DW) mL?1), linoleic acid-β carotene oxidation (74–78 % at 0.8 mg DW mL?1), as well as ferrous ions (EC50 values of 5.0–7.9 mg DW mL?1). Some methodological recommendations regarding the assays used and the expression of results are proposed. 相似文献
60.
Soheir M. El Nahas Mona A. Bibars Dalia A. Taha Hassan I. El-Sayyad 《Journal of Genetic Engineering and Biotechnology》2013,11(1):75-77
The present study investigates CSN1S1 casein gene polymorphism in Egyptian buffalo. CSN1S1 was analyzed in 17 unrelated Egyptian lactating buffalo. The amplified segment includes the last 43 amino acids of Exon 17 and part of Intron 17. In the present study we report for the first time the presence of 2 variants 178Ser (TCA) and 178Leu (TTA) in Egyptian buffalo CSN1S1 gene. The genotypic frequencies in the investigated Egyptian buffalo sample were 0.47, 0.058 and 0.47 for homozygous 178Ser, for homozygous 178Leu and heterozygous 178Leu/Ser, respectively. The 178Ser and 178Leu variant frequencies are 0.64 and 0.36, respectively which indicates the superiority of variant 178Ser in Egyptian buffalo. The allelic frequency in Egyptian buffalo is not much different from the corresponding allelic frequency in Italian buffalo (0.69 and 0.31 for 178Ser and 178Leu, respectively) as reported by Chianese et al. [3]. This is not surprising since they both belong to Mediterranean type. 相似文献