共查询到20条相似文献,搜索用时 15 毫秒
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Paul R. Ortiz de Montellano 《The Journal of biological chemistry》2015,290(36):21833-21844
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Giant viruses are nucleocytoplasmic large DNA viruses (NCLDVs) that infect algae (phycodnaviruses) and amoebae (Mimivirus). We report an unexpected abundance in these giant viruses of islands of bacterial-type genes, including apparently intact prokaryotic mobile genetic elements, and hypothesize that NCLDV genomes undergo successive accretions of bacterial genes. The viruses could acquire bacterial genes within their bacteria-feeding eukaryotic hosts, and we suggest that such acquisition is driven by the intimate coupling of recombination and replication in NCLDVs. 相似文献
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Harold E. Varmus 《Bioscience reports》1990,10(5):413-430
The relationship between retroviral genes and oncogenes is described 相似文献
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Mammalian myosin I alpha, I beta, and I gamma: new widely expressed genes of the myosin I family 总被引:5,自引:0,他引:5
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《The Journal of cell biology》1993,120(6):1405-1416
A polymerase chain reaction strategy was devised to identify new members of the mammalian myosin I family of actin-based motors. Using cellular RNA from mouse granular neurons and PC12 cells, we have cloned and sequenced three 1.2-kb polymerase chain reaction products that correspond to novel mammalian myosin I genes designated MMI alpha, MMI beta, MMI gamma. The pattern of expression for each of the myosin I's is unique: messages are detected in diverse tissues including the brain, lung, kidney, liver, intestine, and adrenal gland. Overlapping clones representing full-length cDNAs for MMI alpha were obtained from mouse brain. These encode a 1,079 amino acid protein containing a myosin head, a domain with five calmodulin binding sites, and a positively charged COOH-terminal tail. In situ hybridization reveals that MMI alpha is highly expressed in virtually all neurons (but not glia) in the postnatal and adult mouse brain and in neuroblasts of the cerebellar external granular layer. Expression varies in different brain regions and undergoes developmental regulation. Myosin I's are present in diverse organisms from protozoa to vertebrates. This and the expression of three novel members of this family in brain and other mammalian tissues suggests that they may participate in critical and fundamental cellular processes. 相似文献
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We developed a multicompartmental Hodgkin-Huxley model of the Hermissenda type-B photoreceptor and used it to address the relative contributions of reductions of two K+ currents, I
a and I
C, to changes in cellular excitability and synaptic strength that occur in these cells after associative learning. We found that reductions of gC, the peak conductance of I
C, substantially increased the firing frequency of the type-B cell during the plateau phase of a simulated light response, whereas reductions of gA had only a modest contribution to the plateau frequency. This can be understood at least in part by the contributions of these currents to the light-induced (nonspiking) generator potential, the plateau of which was enhanced by gC reductions, but not by gA reductions. In contrast, however, reductions of gA broadened the type-B cell action potential, increased Ca2+ influx, and increased the size of the postsynaptic potential produced in a type-A cell, whereas similar reductions of gC had only negligible contributions to these measures. These results suggest that reductions of I
A and I
C play important but different roles in type-B cell plasticity. 相似文献
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Measurement of 131 I and 125 I by liquid scintillation counting 总被引:1,自引:0,他引:1
When aqueous samples are made miscible with a toluene scintillation solution by means of Bio-Solv BBS-3, high 125I and 131I efficiencies can be achieved over a considerable range of “impurity” quenching, and adequate isotope separations can be achieved using liquid scintillation counters with “linear,” “pseudologarithmic,” or “logarithmic” amplification. Using an example of each sort of counter, we have graphically outlined the two somewhat different procedures for choosing the best instrument settings for single- and double-isotope counting. “Linear” instruments, despite a slightly more complex procedure for selection of settings, may offer the advantage, in double-isotope counting, of somewhat greater isotope separations because of the greater attenuation of photo-electron spectra. 相似文献
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Syndapin I and endophilin I bind overlapping proline-rich regions of dynamin I: role in synaptic vesicle endocytosis 总被引:1,自引:1,他引:0
Dynamin I mediates vesicle fission during synaptic vesicle endocytosis (SVE). Its proline-rich domain (PRD) binds the Src-homology 3 (SH3) domain of a subset of proteins that can deform membranes. Syndapin I, amphiphysin I, and endophilin I are its major partners implicated in SVE. Syndapin binding is controlled by phosphorylation at Ser-774 and Ser-778 in the dynamin phospho-box. We now define syndapin and endophilin-binding sites by peptide competition and site-directed mutagenesis. Both bound the same region of the dynamin PRD and both exhibited unusual bidirectional binding modes around core PxxP motifs, unlike amphiphysin which employed a class II binding mode. Endophilin binds to tandem PxxP motifs in the sequence (778)SPTPQRRAPAVPPARPGSR(796) in dynamin, with SPTPQ being an overhang sequence. In contrast, syndapin binding involves two components in the region (772)RRSPTSSPTPQRRAPAVPPARPGSR(796). It required a single PxxP core and a non-PxxP N-terminally anchored extension which bridges the phospho-box and may contribute to binding specificity and affinity. Syndapin binding is exquisitely sensitive to the introduction of negative charges almost anywhere along this region, explaining why it is a highly tuned phospho-sensor. Over-expression of dynamin point mutants that fail to bind syndapin or endophilin inhibit SVE in cultured neurons. Due to overlapping binding sites the interactions between dynamin and syndapin or endophilin were mutually exclusive. Because syndapin acts as a phospho-sensor, this supports its role in depolarization-induced SVE at the synapse, which involves dynamin dephosphorylation. We propose syndapin and endophilin function either at different stages during SVE or in mechanistically distinct types of SVE. 相似文献
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We have generated mice lacking synaptogyrin I and synaptophysin I to explore the functions of these abundant tyrosine-phosphorylated proteins of synaptic vesicles. Single and double knockout mice were alive and fertile without significant morphological or biochemical changes. Electrophysiological recordings in the hippocampal CA1 region revealed that short-term and long-term synaptic plasticity were severely reduced in the synaptophysin/synaptogyrin double knockout mice. LTP was decreased independent of the induction protocol, suggesting that the defect in LTP was not caused by insufficient induction. Our data show that synaptogyrin I and synaptophysin I perform redundant and essential functions in synaptic plasticity without being required for neurotransmitter release itself. 相似文献