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111.
Gellan lyase was purified from the culture fluid of soil samples incubated in a medium containing gellan as a sole carbon source. The enzyme was a monomer with a molecular mass of 140 kDa and was most active at pH 7.5 and 45 degrees C. The enzyme was highly specific to gellan and lowered the viscosity of the polymer. 相似文献
112.
JAK2 associates with the beta c chain of the receptor for granulocyte-macrophage colony-stimulating factor, and its activation requires the membrane-proximal region. 总被引:32,自引:10,他引:22 下载免费PDF全文
F W Quelle N Sato B A Witthuhn R C Inhorn M Eder A Miyajima J D Griffin J N Ihle 《Molecular and cellular biology》1994,14(7):4335-4341
The high-affinity receptor for granulocyte-macrophage colony-stimulating factor (GM-CSF) consists of a unique alpha chain and a beta c subunit that is shared with the receptors for interleukin-3 (IL-3) and IL-5. Two regions of the beta c chain have been defined; these include a membrane-proximal region of the cytoplasmic domain that is required for mitogenesis and a membrane-distal region that is required for activation of Ras, Raf-1, mitogen-activated protein kinase, and S6 kinase. Recent studies have implicated the cytoplasmic protein tyrosine kinase JAK2 in signalling through a number of the cytokine receptors, including the IL-3 and erythropoietin receptors. In the studies described here, we demonstrate that GM-CSF stimulation of cells induces the tyrosine phosphorylation of JAK2 and activates its in vitro kinase activity. Mutational analysis of the beta c chain demonstrates that only the membrane-proximal 62 amino acids of the cytosolic domain are required for JAK2 activation. Thus, JAK2 activation is correlated with induction of mitogenesis but does not, alone, activate the Ras pathway. Carboxyl truncations of the alpha chain, which inactivate the receptor for mitogenesis, are unable to mediate GM-CSF-induced JAK2 activation. Using baculovirus-expressed proteins, we further demonstrate that JAK2 physically associates with the beta c chain but not with the alpha chain. Together, the results further support the hypothesis that the JAK family of kinase are critical to coupling cytokine binding to tyrosine phosphorylation and ultimately mitogenesis. 相似文献
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114.
Distribution of Vacuolar H+-Pyrophosphatase and a Membrane Integral Protein in a Variety of Green Plants 总被引:2,自引:0,他引:2
Vacuolar membranes isolated from several species including fernand moss exhibited pyro-phosphate-dependent H+ transport activity.On immunoblot analysis, H+ -pyrophosphatase was detected inthe vacuolar membranes. A membrane integral protein of 23,000daltons was not found in the membranes of Chara, Conocephalum,or Kalanchoë. Thus, H+-pyrophosphatase may be a universalenzyme among green plants, but the 23-kDa protein is not a commonprotein of central vacuoles. (Received September 10, 1993; Accepted November 29, 1993) 相似文献
115.
A cis-acting element and a trans-acting factor involved in the wound-induced expression of a horseradish peroxidase gene 总被引:2,自引:0,他引:2
Akiyoshi Kawaoka Tomohiro Kawamoto Masami Sekine Kazuya Yoshida Mitsuo Takano Atsuhiko Shinmyo 《The Plant journal : for cell and molecular biology》1994,6(1):87-97
The mechanisms that control the wound-induced expression of the prxC2 gene for horseradish peroxidase (HRP) have been investigated. Analysis of the regulatory properties of 5′-deleted promoters showed that a positive element involved in the response to wounding was located between −307 and −99 bp from the site of initiation of translation. In in vitro binding assays of tobacco nuclear proteins and DNA fragments of prxC2 promoter, the binding site was the Box 1 from −296 to −283 containing the CACGTG motif. To identify the functional role of Box 1, the prxC2 promoter that has been digested from the 5′ end to −289 with a disrupted Box 1 was fused to a reporter gene for β-glucuronidase (GUS). No induction of GUS activity was observed in transgenic tobacco plants with the prxC2(−289)/GUS construct. These data indicated that the expression of prxC2 in response to wounding required the Box 1 sequence from −296 to −283. Furthermore, a tobacco cDNA expression library was screened and a cDNA clone for a protein, designated TFHP-1, that bound specifically to the Box 1 sequence was identified. The putative TFHP-1 protein contains a basic region and leucine zipper (bZip) motif and a helix—loop—helix (HLH) motif. The mRNA for TFHP-1 was abundant in roots and stems, and it was not induced by wounding in leaves. In tobacco protoplasts, antisense TFHP-1 suppressed the expression of prxC2 (−529)/GUS. 相似文献
116.
Taishin Nomura Shunsuke Sato Shinji Doi Jose P. Segundo Michael D. Stiber 《Biological cybernetics》1994,72(1):55-67
The Bonhoeffer-van der Pol (BVP) oscillator is a valuable dynamical system model of pacemaker neurons. Isochrons, phase transition curves (PTC), and two dimensional bifurcation diagrams served to analyze the neuron's response to periodic pulse stimuli. Responses are described and explained in terms of the nonlinear dynamical system theory. An important issue in the generation of spikes by pacemaker neurons is the existence of both slow and fast dynamics in the state point's trajectory in the phase plane. It is this feature in particular that makes the BVP oscillator a faithful model of living pacemaker neurons. Comparison of the model's responses with those of a living pacemaker was based also on return maps of interspike intervals. Analyzed in detail were the complex discharges called stammering which involve interspike intervals that arise unpredictably and exhibit histograms with several modes separated by the equal intervals.Supported by Trent H. Wells Jr. Inc. 相似文献
117.
High pressure conditions stimulate expression of chloramphenicol acetyltransferase regulated by the lac promoter in Escherichia coli 总被引:1,自引:0,他引:1
Chiaki Kato Takako Sato Maria Smorawinska Koki Horikoshi 《FEMS microbiology letters》1994,122(1-2):91-96
Abstract Recombinant plasmids with the chloramphenicol acetyltransferase (CAT) structural gene behind several kinds of promoters were tested for expression in Escherichia coli during growth at atmospheric pressure (0.1 MPa) and at high pressure (30 MPa). Expression of the CAT gene from the lac promoter was remarkably activated (approx. 78-fold) by high pressure in the absence of the inducer isopropyl-β-d-thiogalactopyranoside (IPTG). The stimulation of the CAT activity by the lac promoter at high pressure did not simply result from an increased plasmid copy number, because the CAT activities from the other promoters and β-lactamase activities were unaffected at high pressure. 相似文献
118.
Hideaki Sato Hideki Hirayama Takeshi Yamamoto Yoshimasa Lchio Fumiaki Ishizawa Michinao Mizugaki 《Luminescence》1994,9(2):73-77
The purpose of the study was to evaluate the quality of Toki-shakuyaku-san extract granules (TJ-23) using chemiluminescence (CL). A linear relationship was obtained between the log value of the CL of TJ-23 and the reaction temperature. An excellent correlation (r= 0.999) was found between the slope of this curve (ΔA) and the colour intensity due to the browning reaction occurring at the early stage of the Maillard reaction. 相似文献
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120.