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排序方式: 共有660条查询结果,搜索用时 15 毫秒
61.
Chandra A Grecco HE Pisupati V Perera D Cassidy L Skoulidis F Ismail SA Hedberg C Hanzal-Bayer M Venkitaraman AR Wittinghofer A Bastiaens PI 《Nature cell biology》2012,14(2):148-158
We identify a role for the GDI-like solubilizing factor (GSF) PDEδ in modulating signalling through Ras family G proteins by sustaining their dynamic distribution in cellular membranes. We show that the GDI-like pocket of PDEδ binds and solubilizes farnesylated Ras proteins, thereby enhancing their diffusion in the cytoplasm. This mechanism allows more effective trapping of depalmitoylated Ras proteins at the Golgi and polycationic Ras proteins at the plasma membrane to counter the entropic tendency to distribute these proteins over all intracellular membranes. Thus, PDEδ activity augments K/Hras signalling by enriching Ras at the plasma membrane; conversely, PDEδ down-modulation randomizes Ras distributions to all membranes in the cell and suppresses regulated signalling through wild-type Ras and also constitutive oncogenic Ras signalling in cancer cells. Our findings link the activity of PDEδ in determining Ras protein topography to Ras-dependent signalling. 相似文献
62.
A V Glazunov V M Glazer D R Perera A V Bore?ko 《Molekuliarnaia genetika, mikrobiologiia i virusologiia》1987,(8):19-25
The efficiency of "LiCl transformation" in Saccharomyces cerevisiae haploid cells by an autonomously replicating pLL12 plasmid carrying yeast LEU2 and LYS2 genes is increased (by an order or more) when the plasmid is linearized by the restriction endonuclease XhoI cleavage of a unique site in LYS2 gene. Transformants were selected on the medium lacking leucine. This phenomenon has been shown to be a result of recombinational repair of double-strand breaks (DSB) of plasmid DNA stimulated by a restriction endonuclease. The kinetic data have shown the process of plasmid DNA DSB repair to consist of two phases. The completion of the first phase occurs during an hour and the second phase occurs in 14-18 hours. DNA double-strand gaps (the deleted sequences of plasmid LYS2 gene in DSB region) with maximal length of 2-2.5 kb are repaired with the same efficiency as DSB. The genetic control of the recombinational repair of plasmid DNA DSB has been studied. 相似文献
63.
Laura Corrigan Siamak Redhai Aaron Leiblich Shih-Jung Fan Sumeth M.W. Perera Rachel Patel Carina Gandy S. Mark Wainwright John F. Morris Freddie Hamdy Deborah C.I. Goberdhan Clive Wilson 《The Journal of cell biology》2014,206(5):671-688
Male reproductive glands secrete signals into seminal fluid to facilitate reproductive success. In Drosophila melanogaster, these signals are generated by a variety of seminal peptides, many produced by the accessory glands (AGs). One epithelial cell type in the adult male AGs, the secondary cell (SC), grows selectively in response to bone morphogenetic protein (BMP) signaling. This signaling is involved in blocking the rapid remating of mated females, which contributes to the reproductive advantage of the first male to mate. In this paper, we show that SCs secrete exosomes, membrane-bound vesicles generated inside late endosomal multivesicular bodies (MVBs). After mating, exosomes fuse with sperm (as also seen in vitro for human prostate-derived exosomes and sperm) and interact with female reproductive tract epithelia. Exosome release was required to inhibit female remating behavior, suggesting that exosomes are downstream effectors of BMP signaling. Indeed, when BMP signaling was reduced in SCs, vesicles were still formed in MVBs but not secreted as exosomes. These results demonstrate a new function for the MVB–exosome pathway in the reproductive tract that appears to be conserved across evolution. 相似文献
64.
Dominik Sakry Angela Neitz Jeet Singh Renato Frischknecht Daniele Marongiu Fabien Binamé Sumudhu S. Perera Kristina Endres Beat Lutz Konstantin Radyushkin Jacqueline Trotter Thomas Mittmann 《PLoS biology》2014,12(11)
The role of glia in modulating neuronal network activity is an important question. Oligodendrocyte precursor cells (OPC) characteristically express the transmembrane proteoglycan nerve-glia antigen 2 (NG2) and are unique glial cells receiving synaptic input from neurons. The development of NG2+ OPC into myelinating oligodendrocytes has been well studied, yet the retention of a large population of synapse-bearing OPC in the adult brain poses the question as to additional functional roles of OPC in the neuronal network. Here we report that activity-dependent processing of NG2 by OPC-expressed secretases functionally regulates the neuronal network. NG2 cleavage by the α-secretase ADAM10 yields an ectodomain present in the extracellular matrix and a C-terminal fragment that is subsequently further processed by the γ-secretase to release an intracellular domain. ADAM10-dependent NG2 ectodomain cleavage and release (shedding) in acute brain slices or isolated OPC is increased by distinct activity-increasing stimuli. Lack of NG2 expression in OPC (NG2-knockout mice), or pharmacological inhibition of NG2 ectodomain shedding in wild-type OPC, results in a striking reduction of N-methyl-D-aspartate (NMDA) receptor-dependent long-term potentiation (LTP) in pyramidal neurons of the somatosensory cortex and alterations in the subunit composition of their α-amino-3-hydroxy-5-methyl-4-isoxazolepr opionicacid (AMPA) receptors. In NG2-knockout mice these neurons exhibit diminished AMPA and NMDA receptor-dependent current amplitudes; strikingly AMPA receptor currents can be rescued by application of conserved LNS protein domains of the NG2 ectodomain. Furthermore, NG2-knockout mice exhibit altered behavior in tests measuring sensorimotor function. These results demonstrate for the first time a bidirectional cross-talk between OPC and the surrounding neuronal network and demonstrate a novel physiological role for OPC in regulating information processing at neuronal synapses. 相似文献
65.
Marina Lpez‐Pozo Jaume Flexas Javier Gulías Marc Carriquí Miquel Nadal Alicia V. Perera‐Castro María Jos Clemente‐Moreno Jorge Gago Encarnacin Núez‐Olivera Javier Martínez‐Abaigar Antonio Hernndez Unai Artetxe Joanne Bentley Jill M. Farrant Amy Verhoeven Jos Ignacio García‐Plazaola Beatriz Fernndez‐Marín 《Physiologia plantarum》2019,167(4):540-555
Desiccation tolerant (DT) plants withstand complete cellular dehydration, reaching relative water contents (RWC) below 30% in their photosynthetic tissues. Desiccation sensitive (DS) plants exhibit different degrees of dehydration tolerance (DHT), never surviving water loss >70%. To date, no procedure for the quantitative evaluation of DHT extent exists that is able to discriminate DS species with differing degrees of DHT from truly DT plants. We developed a simple, feasible and portable protocol to differentiate between DT and different degrees of DHT in the photosynthetic tissues of seed plants and between fast desiccation (< 24 h) tolerant (FDT) and sensitive (FDS) bryophytes. The protocol is based on (1) controlled desiccation inside Falcon tubes equilibrated at three different relative humidities that, consequently, induce three different speeds and extents of dehydration and (2) an evaluation of the average percentage of maximal photochemical efficiency of PSII (Fv/fm) recovery after rehydration. Applying the method to 10 bryophytes and 28 tracheophytes from various locations, we found that (1) imbibition of absorbent material with concentrated salt‐solutions inside the tubes provides stable relative humidity and avoids direct contact with samples; (2) for 50 ml capacity tubes, the optimal plant amount is 50–200 mg fresh weight; (3) the method is useful in remote locations due to minimal instrumental requirements; and (4) a threshold of 30% recovery of the initial Fv/fm upon reaching RWC ≤ 30% correctly categorises DT species, with three exceptions: two poikilochlorophyllous species and one gymnosperm. The protocol provides a semi‐quantitative expression of DHT that facilitates comparisons of species with different morpho‐physiological traits and/or ecological attributes. 相似文献
66.
The P4 metal binding site in RNase P RNA affects active site metal affinity through substrate positioning 总被引:1,自引:0,他引:1
Although helix P4 in the catalytic domain of the RNase P ribozyme is known to coordinate magnesium ions important for activity, distinguishing between direct and indirect roles in catalysis has been difficult. Here, we provide evidence for an indirect role in catalysis by showing that while the universally conserved bulge of helix P4 is positioned 5 nt downstream of the cleavage site, changes in its structure can still purturb active site metal binding. Because changes in helix P4 also appear to alter its position relative to the pre-tRNA cleavage site, these data suggest that P4 contributes to catalytic metal ion binding through substrate positioning. 相似文献
67.
Evolutionary history of Trachylepis skinks in the Seychelles islands: introgressive hybridization,morphological evolution and geographic structure 下载免费PDF全文
Sara Rocha Anna Perera Andreia Silva David Posada D. James Harris 《Biological journal of the Linnean Society. Linnean Society of London》2016,119(1):15-36
The Seychelles is a remarkably interesting archipelago for evolutionary studies, but only recently have molecular markers been used to explore its biogeographic patterns. Here we used morphological and molecular data to examine diversity and phylogenetic relationships of two endemic skink sister‐species from this archipelago: Trachylepis sechellensis and Trachylepis wrightii. Mitochondrial DNA genealogy rendered a monophyletic T. wrightii nested within a paraphyletic T. sechellensis, whereas nuclear DNA sequences from five unlinked markers reflected the accepted taxonomy. Hybridization and massive mtDNA introgression leading to the complete replacement of the native mtDNA lineage of T. sechellensis in some of the islands were invoked to explain this result, and morphological variation also seemed to reflect this pattern of reticulation. A Mio‐Pliocene divergence between both species is suggested. Multilocus molecular data were used to uncover biogeographic patterns within the archipelago, which reflected shared patterns with other co‐distributed lizard taxa; specifically a north–south marked structure, a close relationship between populations from Fregate and the southern islands, and a detectable isolation within the southern group, between Mahé, and Silhouette and North Islands. Gene flow from these latter islands towards the northern group was also suggested. These results add to the growing body of evidence of the influence of geographic distance and sea‐level oscillations in shaping the genetic structure of Seychellois taxa and of the existence of common biogeographic patterns across the archipelago. 相似文献
68.
Margaret C. Gawienowski Daniel Szymanski Imara Y. Perera Raymond E. Zielinski 《Plant molecular biology》1993,22(2):215-225
Three new, unique cDNA sequences encoding isoforms of calmodulin (CaM) were isolated from an Arabidopsis cDNA library cloned in gt10. These sequences (ACaM-4, -5, and -6) represent members of the Arabidopsis CaM gene family distinct from the three DNA sequences previously reported. ACaM-4 and -6 encode full-length copies of CaM mRNAs of ca. 0.75 kb. The ACaM-5 sequence encodes a partial length copy of CaM mRNA that is lacking sequences encoding the amino-terminal 10 amino acids of mature CaM and the initiator methionine. The derived amino acid sequence of ACaM-5 is identical to the sequences encoded by two of the previously characterized ACaM cDNAs, and is identical to TCH-1 mRNA, whose accumulation was increased by touch stimulation. The polypeptides encoded by ACaM-4 and -6 differ from that encoded by ACaM-5 by six and two amino acid substititions, respectively. Most of the deduced amino acid sequence substitutions in the Arabidopsis CaM isoforms occurred in the fourth Ca2+-binding domain. Polymerase chain reaction amplification assays of ACaM-4, -5 and -6 mRNA sequences indicated that each accumulated in Arabidopsis leaf RNA fractions, but only ACaM-4 and -5 mRNAs were detected in silique total RNA. The six different CaM cDNA sequences each hybridize with unique Eco RI restriction fragments in genomic Southern blots of Arabidopsis DNA, indicating that these sequences were derived from distinct structural genes. Our results suggest that CaM isoforms in Arabidopsis may have evolved to optimize the interaction of this Ca2+-receptor protein with specific subsets of response elements. 相似文献
69.
Antigoni Kaliontzopoulou Dean C. Adams Arie van der Meijden Ana Perera Miguel A. Carretero 《Evolutionary ecology》2012,26(4):825-845
Understanding the relationship between form and function is central to our comprehension of how phenotypic diversity evolves. Traits involved in multiple activities, such as social interactions and ecological resource use, are under the influence of different evolutionary forces potentially acting in opposite directions. Such systems provide the opportunity of understanding how potential constraints on morphological variation may influence whole-organism performance. In this study we examined morphology and bite performance in two closely related species of Podarcis wall lizards with divergent microhabitat preferences, to investigate how natural and sexual selection interact to shape the evolution of head traits. Our results show that although head morphology is markedly different between species and sexes, only sexes differ in bite force, indicating that the ecological differentiation between species is reflected in their morphology but does not constrain performance. Rather, the modification of the relative size of head components between species and a shift in the form-function relationship provide a potential explanation of how equal performance is attained by different morphological configurations. Geometric morphometrics provide a clear, biomechanically meaningful image of how this is achieved and show a bisexual pattern of head shape-bite force association in both species. This, together with a strong allometry of head size on body size and head shape on head size, provides indirect morphological evidence for the importance of sexual selection in shaping morphological and functional patterns. Finally, our findings suggest that the differences observed between species and sexes in head traits and bite performance are not reflected in their dietary ecology, implying that if trophic niche segregation between groups occurs, the reasons behind it are not primarily related to head morphology and functional variation. 相似文献
70.
Chandima Jeewandara Thiruni N. Adikari Laksiri Gomes Samitha Fernando R. H. Fernando M. K. T. Perera Dinuka Ariyaratne Achala Kamaladasa Maryam Salimi Shamini Prathapan Graham S. Ogg Gathsaurie Neelika Malavige 《PLoS neglected tropical diseases》2015,9(4)