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81.
RimM and RbfA Are Essential for Efficient Processing of 16S rRNA in Escherichia coli 总被引:2,自引:0,他引:2 下载免费PDF全文
Gran O. Bylund L. Charlotta Wipemo L. A. Carina Lundberg P. Mikael Wikstrm 《Journal of bacteriology》1998,180(1):73-82
The trmD operon is located at 56.7 min on the genetic map of the Escherichia coli chromosome and contains the genes for ribosomal protein (r-protein) S16, a 21-kDa protein (RimM, formerly called 21K), the tRNA (m1G37)methyltransferase (TrmD), and r-protein L19, in that order. Previously, we have shown that strains from which the rimM gene has been deleted have a sevenfold-reduced growth rate and a reduced translational efficiency. The slow growth and translational deficiency were found to be partly suppressed by mutations in rpsM, which encodes r-protein S13. Further, the RimM protein was shown to have affinity for free ribosomal 30S subunits but not for 30S subunits in the 70S ribosomes. Here we have isolated several new suppressor mutations, most of which seem to be located close to or within the nusA operon at 68.9 min on the chromosome. For at least one of these mutations, increased expression of the ribosome binding factor RbfA is responsible for the suppression of the slow growth and translational deficiency of a ΔrimM mutant. Further, the RimM and RbfA proteins were found to be essential for efficient processing of 16S rRNA. 相似文献
82.
Two taxa are usually recognized in Scandinavian Pseudorchis albida s.1. (Orchidaceae), the lowland to subalpine P. albida s.s., and the alpine P. straminea . We used allozymes to study the genetical differentiation within and among populations and taxa. Four populations of P. albida s.s. and two populations of P. straminea , all from Sweden, were included in the study. Eighteen loci of thirteen different enzyme systems were analyzed. Five loci were variable within, or between, the taxa. The taxa had different alleles at one of the five variable loci, whereas there was overlap at four loci. In all, 22 different alleles were found. Two of these alleles were confined to P. albida s.s., while four alleles were confined to P. straminea . In P. albida s.s., one locus out of 15 (6.7 %) was polymorphic. In P. straminea , three loci out of 18 (16.7 %) were polymorphic. In both taxa, the average number of alleles per polymorphic locus was 2.0 (each polymorphic locus had two alleles). Nei's genetic identity was 0.81 between taxa, and about 1 among populations of P. albida s.s., while the identity between the two populations of P. straminea was 0.98. Although the differentiation is small, present-day distributions of taxa suggest that the divergence probably started before the Weichselian glaciation. The low within-taxon and within-population variation in Scandinavia may be due to ancient founder events. The association of P. albida s.s. with anthropogenic hay-meadows and open woodland and the association of P. straminea with open mountain habitats suggest that taxa may have immigrated into Scandinavia at different times. 相似文献
83.
Bruno Chauffert Marie-Thérèse Dimanche-Boitrel Carmen Garrido Mikael Ivarsson Monique Martin François Martin Eric Solary 《Cytotechnology》1998,27(1-3):225-235
Kinetic resistance plays a major role in the failure of chemotherapy towards many solid tumors. Kinetic resistance to cytotoxic
drugs can be reproduced in vitro by growing the cells as multicellular spheroids (Multicellular Resistance) or as hyperconfluent
cultures (Confluence-Dependent Resistance). Recent findings on the cell cycle regulation have permitted a better understanding
why cancer cells which arrest in long quiescent phases are poorly sensitive to cell-cycle specific anticancer drugs. Two cyclin-dependent
kinase inhibitors (CDKI) seem particularly involved in the cell cycle arrest at the G1 to S transition checkpoint: the p53-dependent
p21cip1 protein which is activated by DNA damage and the p27kip1 which is a mediator of the contact inhibition signal. Cell quiescence could alter drug-induced apoptosis which is partly
dependent on an active progression in the cell cycle and which is facilitated by overexpression of oncogenes such as c-Myc
or cyclins. Investigations are yet necessary to determine the influence of the cell cycle on the balance between antagonizing
(bcl-2, bcl-XL...) or stimulating (Bax, Bcl-XS, Fas...) factors in chemotherapy-induced apoptosis. Quiescent cells could also be protected from toxic agents by an enhanced
expression of stress proteins, such as HSP27 which is induced by confluence. New strategies are required to circumvent kinetic
resistance of solid tumors: adequate choice of anticancer agents whose activity is not altered by quiescence (radiation, cisplatin),
recruitment from G1 to S/G2 phases by cell pretreatment with alkylating drugs or attenuation of CDKI activity by specific
inhibitors.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
84.
Saara Laulumaa Tuomo Nieminen Mari Lehtim?ki Shweta Aggarwal Mikael Simons Michael M. Koza Ilpo Vattulainen Petri Kursula Francesca Natali 《PloS one》2015,10(6)
Myelin protein P2 is a fatty acid-binding structural component of the myelin sheath in the peripheral nervous system, and its function is related to its membrane binding capacity. Here, the link between P2 protein dynamics and structure and function was studied using elastic incoherent neutron scattering (EINS). The P38G mutation, at the hinge between the β barrel and the α-helical lid, increased the lipid stacking capacity of human P2 in vitro, and the mutated protein was also functional in cultured cells. The P38G mutation did not change the overall structure of the protein. For a deeper insight into P2 structure-function relationships, information on protein dynamics in the 10 ps to 1 ns time scale was obtained using EINS. Values of mean square displacements mainly from protein H atoms were extracted for wild-type P2 and the P38G mutant and compared. Our results show that at physiological temperatures, the P38G mutant is more dynamic than the wild-type P2 protein, especially on a slow 1-ns time scale. Molecular dynamics simulations confirmed the enhanced dynamics of the mutant variant, especially within the portal region in the presence of bound fatty acid. The increased softness of the hinge mutant of human myelin P2 protein is likely related to an enhanced flexibility of the portal region of this fatty acid-binding protein, as well as to its interactions with the lipid bilayer surface requiring conformational adaptations. 相似文献
85.
Relationship between lifestyle behaviors and obesity in children ages 9–11: Results from a 12‐country study 下载免费PDF全文
Peter T. Katzmarzyk Tiago V. Barreira Stephanie T. Broyles Catherine M. Champagne Jean‐Philippe Chaput Mikael Fogelholm Gang Hu William D. Johnson Rebecca Kuriyan Anura Kurpad Estelle V. Lambert Carol Maher Jose Maia Victor Matsudo Timothy Olds Vincent Onywera Olga L. Sarmiento Martyn Standage Mark S. Tremblay Catrine Tudor‐Locke Pei Zhao Timothy S. Church for the ISCOLE Research Group 《Obesity (Silver Spring, Md.)》2015,23(8):1696-1702
86.
Heli Elovaara Teija Huusko Mikael Maksimow Kati Elima Gennady G. Yegutkin Mikael Skurnik Ulrich Dobrindt Anja Siitonen Michael J. McPherson Marko Salmi Sirpa Jalkanen 《PloS one》2015,10(11)
Escherichia coli amine oxidase (ECAO), encoded by the tynA gene, catalyzes the oxidative deamination of aromatic amines into aldehydes through a well-established mechanism, but its exact biological role is unknown. We investigated the role of ECAO by screening environmental and human isolates for tynA and characterizing a tynA-deletion strain using microarray analysis and biochemical studies. The presence of tynA did not correlate with pathogenicity. In tynA+ Escherichia coli strains, ECAO enabled bacterial growth in phenylethylamine, and the resultant H2O2 was released into the growth medium. Some aminoglycoside antibiotics inhibited the enzymatic activity of ECAO, which could affect the growth of tynA+ bacteria. Our results suggest that tynA is a reserve gene used under stringent environmental conditions in which ECAO may, due to its production of H2O2, provide a growth advantage over other bacteria that are unable to manage high levels of this oxidant. In addition, ECAO, which resembles the human homolog hAOC3, is able to process an unknown substrate on human leukocytes. 相似文献
87.
A heterozygosity–fitness correlations (HFCs) may reflect inbreeding depression, but the extent to which they do so is debated. HFCs are particularly likely to occur after demographic disturbances such as population bottleneck or admixture. We here study HFC in an introduced and isolated ungulate population of white‐tailed deer Odocoileus virginianus in Finland founded in 1934 by four individuals. A total of 422 ≥ 1‐year‐old white‐tailed deer were collected in the 2012 hunting season in southern Finland and genotyped for 14 microsatellite loci. We find significant identity disequilibrium as estimated by g2. Heterozygosity was positively associated with size‐ and age‐corrected body mass, but not with jaw size or (in males) antler score. Because of the relatively high identity disequilibrium, heterozygosity of the marker panel explained 51% of variation in inbreeding. Inbreeding explained approximately 4% of the variation in body mass and is thus a minor, although significant source of variation in body mass in this population. The study of HFC is attractive for game‐ and conservation‐oriented wildlife management because it presents an affordable and readily used approach for genetic monitoring that allowing identification of fitness costs associated with genetic substructuring in what may seem like a homogeneous population. 相似文献
88.
Sing-Huang Tan Nur Sabrina Sapari Hui Miao Mikael Hartman Marie Loh Wee-Joo Chng Philip Iau Shaik Ahmad Buhari Richie Soong Soo-Chin Lee 《PloS one》2015,10(12)
Background
Changes in tumor DNA mutation status during chemotherapy can provide insights into tumor biology and drug resistance. The purpose of this study is to analyse the presence or absence of mutations in cancer-related genes using baseline breast tumor samples and those obtained after exposure to one cycle of chemotherapy to determine if any differences exist, and to correlate these differences with clinical and pathological features.Methods
Paired breast tumor core biopsies obtained pre- and post-first cycle doxorubicin (n = 18) or docetaxel (n = 22) in treatment-naïve breast cancer patients were analysed for 238 mutations in 19 cancer-related genes by the Sequenom Oncocarta assay.Results
Median age of patients was 48 years (range 32–64); 55% had estrogen receptor-positive tumors, and 60% had tumor reduction ≥25% after cycle 1. Mutations were detected in 10/40 (25%) pre-treatment and 11/40 (28%) post-treatment samples. Four mutation pattern categories were identified based on tumor mutation status pre- → post-treatment: wildtype (WT)→WT, n = 24; mutant (MT)→MT, n = 5; MT→WT, n = 5; WT→MT, n = 6. Overall, the majority of tumors were WT at baseline (30/40, 75%), of which 6/30 (20%) acquired new mutations after chemotherapy. Pre-treatment mutations were predominantly in PIK3CA (8/10, 80%), while post-treatment mutations were distributed in PIK3CA, EGFR, PDGFRA, ABL1 and MET. All 6 WT→MT cases were treated with docetaxel. Higher mutant allele frequency in baseline MT tumors (n = 10; PIK3CA mutations n = 8) correlated with less tumor reduction after cycle 1 chemotherapy (R = -0.667, p = 0.035). No other associations were observed between mutation pattern category with treatment, clinicopathological features, and tumor response or survival.Conclusion
Tumor mutational profiles can change as quickly as after one cycle of chemotherapy in breast cancer. Understanding of these changes can provide insights on potential therapeutic options in residual resistant tumors.Trial Registration
ClinicalTrials.gov NCT00212082相似文献89.
Niina Idänheimo Adrien Gauthier Jarkko Salojärvi Riccardo Siligato Mikael Brosché Hannes Kollist Ari Pekka Mähönen Jaakko Kangasjärvi Michael Wrzaczek 《Biochemical and biophysical research communications》2014
Receptor-like kinases are important regulators of many different processes in plants. Despite their large number only a few have been functionally characterized. One of the largest subgroups of receptor-like kinases in Arabidopsis is the cysteine-rich receptor like kinases (CRKs). High sequence similarity among the CRKs has been suggested as major cause for functional redundancy. The genomic localization of CRK genes in back-to-back repeats has made their characterization through mutant analysis unpractical. Expression profiling has linked the CRKs with reactive oxygen species, important signaling molecules in plants. Here we have investigated the role of two CRKs, CRK6 and CRK7, and analyzed their role in extracellular ROS signaling. CRK6 and CRK7 are active protein kinases with differential preference for divalent cations. Our results suggest that CRK7 is involved in mediating the responses to extracellular but not chloroplastic ROS production. 相似文献
90.
The affinity of ionized fatty acids for the Na,K-ATPase is used to determine the transmembrane profile of water penetration at the protein-lipid interface. The standardized intensity of the electron spin echo envelope modulation (ESEEM) from 2H-hyperfine interaction with D2O is determined for stearic acid, n-SASL, spin-labeled systematically at the C-n atoms throughout the chain. In both native Na,K-ATPase membranes from shark salt gland and bilayers of the extracted membrane lipids, the D2O-ESEEM intensities of fully charged n-SASL decrease progressively with position down the fatty acid chain toward the terminal methyl group. Whereas the D2O intensities decrease sharply at the n = 9 position in the lipid bilayers, a much broader transition region in the range n = 6 to 10 is found with Na,K-ATPase membranes. Correction for the bilayer population in the membranes yields the intrinsic D2O-intensity profile at the protein-lipid interface. For positions at either end of the chains, the D2O concentrations at the protein interface are greater than in the lipid bilayer, and the positional profile is much broader. This reveals the higher polarity, and consequently higher intramembrane water concentration, at the protein-lipid interface. In particular, there is a significant water concentration adjacent to the protein at the membrane midplane, unlike the situation in the bilayer regions of this cholesterol-rich membrane. Experiments with protonated fatty acid and phosphatidylcholine spin labels, both of which have a considerably lower affinity for the Na,K-ATPase, confirm these results. 相似文献