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71.
The type 1 insulin-like growth factor receptor (IGF-IR) and its docking protein, insulin receptor substrate-1 (IRS-1), play important roles in cell transformation, cell differentiation and aging. IRS-1 and other IRS proteins can, under certain conditions, localize to the nuclei of cells, where they undergo interactions with nuclear and nucleolar proteins. In this study, we confirm and extend these observations, demonstrating that IRS-1 is preferentially nuclear in growing cells. Differentiation and inhibition of ribosomal RNA synthesis cause subcellular redistribution of IRS-1 and other nuclear proteins to the cytoplasm. 相似文献
72.
73.
高维非自治系统的周期解 总被引:1,自引:0,他引:1
本文通过建立并利用齐次线性方程解的估计公式,获得了周期系统(1)的周期解的存在性、唯一性定理,对周期系统(2)给出了一个平稳振荡定理,最后给出了实例。 相似文献
74.
超低能重离子注入作物育种的原初物理机制 总被引:2,自引:0,他引:2
从原子核物理学观点出发,采用理论分析与实验测量并举的方法对超级能(〈200kev)重离子(Z≥6)注入作物(小麦)种子进行诱变育种的原初物理机制进行了研究,结果表明,无论是注入离子本身的射程,还是次级电子,自由基扩散,高温热穗,级联原子和冲击波等次级作用范围都无法触及表皮下面的胚细胞,但注入离子在麦胚内主要元素(C,N,O,S,P,K,Ca)上激发出的特征X-射线,在其强度减弱为原来的10^-3时 相似文献
75.
76.
The mechanism by which chemical energy is converted into an electrochemical gradient by P-type ATPase is not completely understood. The effects of ATP analogs on the canine kidney (Na++ K+) ATPase were compared to effects of the same analogs on the maize (Zea mays L. cv. W7551) root H+-ATPase in order to identify probes for the ATP binding site of the maize root enzyme and to determine potential similarities of ATP hydrolysis mechanisms in these two enzymes. Six compounds able to modify the ATP binding site covalently were compared. These compounds could be classed into three distinct groups based on activity. The first group had little or no effect on catalytic activity of either enzyme and included 7-chloro-4-nitrobenz-2-oxa-1.3-diazole. The second group, which included azido adenine analogs. fluorescein isothiocyanate and 5′-p-fluorosulfonylbenzoyladenine, were inhibitors of ATP hydrolysis by both enzymes. However, the sensitivity of the (Na++ K+) ATPase to inhibition was much greater than that exhibited by the maize root enzyme. The third group, which included periodate treated nucleotide derivatives and 2′,3′-o-(4-benzoylbenzoyl)adenosine triphosphate. inhibited both enzymes similarly. This initial screening of these covalent modifiers indicated that 2′,3′-o-(4-benzoylbenzoyl)adenosine triphosphate was the optimal covalent modifier of the ATP binding site of the maize root enzyme. Certain reagents were much more effective against the (Na++ K+) ATPase than the maize root enzyme, possibly indicating differences in the ATP binding and hydrolysis pathway for these two enzymes. Two ATP analogs that are not covalent modifiers were also tested: the trinitrophenyl derivatives of adenine nucleotides were better than 5′-adenylylimidodiphosphate for use as an ATP binding probe. 相似文献
77.
REG1 binds to protein phosphatase type 1 and regulates glucose repression in Saccharomyces cerevisiae. 总被引:12,自引:2,他引:10
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Protein phosphatase type 1 (PP1) is encoded by GLC7, an essential gene in Saccharomyces cerevisiae. The GLC7 phosphatase is required for glucose repression and appears to function antagonistically to the SNF1 protein kinase. Previously, we characterized a mutation, glc7-T152K, that relieves glucose repression but does not interfere with the function of GLC7 in glycogen metabolism. We proposed that the mutant GLC7T152K phosphatase is defective in its interaction with a regulatory subunit that directs participation of PP1 in the glucose repression mechanism. Here, we present evidence that REG1, a protein required for glucose repression, is one such regulatory subunit. We show that REG1 is physically associated with GLC7. REG1 interacts with GLC7 strongly and specifically in the two-hybrid system, and REG1 and GLC7 fusion proteins co-immunoprecipitate from cell extracts. Moreover, overexpression of a REG1 fusion protein suppresses the glc7-T152K mutant defect in glucose repression. This and other genetic evidence indicate that the two proteins function together in regulating glucose repression. These results suggest that REG1 is a regulatory subunit of PP1 that targets its activity to proteins in the glucose repression regulatory pathway. 相似文献
78.
A link between increased transforming activity of lymphoma-derived MYC mutant alleles, their defective regulation by p107, and altered phosphorylation of the c-Myc transactivation domain. 总被引:5,自引:4,他引:1
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A T Hoang B Lutterbach B C Lewis T Yano T Y Chou J F Barrett M Raffeld S R Hann C V Dang 《Molecular and cellular biology》1995,15(8):4031-4042
79.
Shui-Tein Chen Shiah-Yun Chen Chen-Chen Tu Shyh-Horng Chiou Kung-Tsung Wang 《Journal of Protein Chemistry》1995,14(4):205-215
The alkaline proteases subtilisin Carlsberg and alcalase possess substantial enzymatic activity even when dissolved in ethanol. The crude enzymes were purified by gel filtration and the main fractions suspended in ethanol to give a translucent suspension. Both the supernatant and the resuspended precipitate after high-speed centrifugation were found to have enzymatic activities. The solubility of subtilisin Carlsberg in anhydrous ethanol was found to be 45.1g/ml and that of alcalase was 48.1g/ml by Coomassie blue dye-binding method using bovine serum albumin as a standard. In the presence of water, the solubility of both enzymes increased with water content. The stability of enzymes incubated in ethanol was assayed by their amidase and transesterase activities using Ala-Ala-Pro-Phe-pNA as substrate in phosphate buffer (pH8.2) and Moz-Leu-OBzl as substrate in anhydrous ethanol, respectively. The soluble enzymes have a half-life of about 36 hr and that of suspended enzymes about 50 hr in the amidase activity assay, whereas the same soluble enzymes have a half-life of about several hours and that of suspended enzymes 1 h by the transesterase activity assay. The stability of both enzymes decreased as water concentration increased. The diastereoselectivity of the enzyme-catalyzed hydrolysis of diastereo pairs of tetrapeptide esters,l-Ala-l-Ala-(d-orl-)Pro-l-Phe-OMe andl-Ala-l-Ala-(d-orl-)Ala-l-Phe-OMe, in phosphate is as high as that of the transesterification of these substrates in ethanol. It is concluded that active sites and selectivity of alkaline serine proteases in anhydrous alcohol are probably very similar to those in aqueous solution in spite of the fact that a lower reactivity is usually associated with the enzymes in nonaqueous solvents. 相似文献
80.
On the production,elemental composition (C,N, P) and distribution of photosynthetic organic matter in the Southern Black Sea 总被引:2,自引:1,他引:1
Yılmaz Ayşen Tuğrul Süleyman Polat Çolpan Ediger Dilek Çoban Yeşim Morkoç Enis 《Hydrobiologia》1997,363(1-3):141-155
Chemical oceanographic understanding of the southernBlack Sea has been improved by recent measurements ofthe optical transparency,
phytoplankton biomass (interms of chlorophyll-a and particulate organic matter)and primary productivity. During the spring-autmunperiod
of 1995–1996, light generally penetrated onlyinto the upper 15–40 m, with an attenuation coefficientvarying between 0.125
and 0.350 m2122;1. The averagechlorophyll-a (Chl-a) concentrations for the euphoticzone ranged from 0.1 to 1.5 μg l2122;1. Coherentsub-surface Chl-a maxima were formed near the base ofthe euphotic zone only in summer. Production rate variedbetween
247 and 1925 in the spring and between 405 and687 mgC m2122;2 d2122;1 in the summer-autumn period.The average POM concentrations in the euphotic zonevaried regionally and seasonally between 3.8
and28.6 μm for POC, 0.5 and 3.1 μm for PON and0.02 and 0.1 μm for PP. Atomic ratios of C/N, C/Pand N/P, derived from the regressions
of POM data,ranged between 7.5 and 9.6, 109 and 165, and 11.2 and16.6, respectively. In the suboxic/anoxic interface,the elemental
ratios change substantially due to anaccumulation of PP cohering to Fe and Mn oxides. Thechemocline boundaries and the distinct
chemicalfeatures of the oxic/anoxic transition layer (the so-called suboxic zone) are all located at specificdensity surfaces;
however, they exhibit remarkablespatial and temporal variations both in their positionand in their magnitude, which permit
the definition of long-term changes in the biochemical properties of theBlack Sea upper layer.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献