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991.
植物SUMO化修饰及其生物学功能 总被引:2,自引:0,他引:2
SUMO化修饰是细胞内蛋白质功能调节的重要方式之一。植物中的SUMO化修饰途径由SUMO分子和SUMO化酶系组成。SUMO化修饰是一个可逆的动态过程。SUMO前体蛋白在SUMO特异性蛋白酶的作用下成熟,随后通过SUMO活化酶、SUMO结合酶和SUMO连接酶将靶蛋白SUMO化,最后SUMO特异性蛋白酶将SUMO与靶蛋白分离,重新进入SUMO化循环。初步研究表明,植物SUMO化修饰参与植物花期调控、激素信号转导、抗病防御以及逆境应答等生理过程。 相似文献
992.
Liu Y Fu X Shen J Zhang H Hong W Chang Z 《Biochemical and biophysical research communications》2004,316(3):795-801
Periplasmic proteins of Gram-negative bacteria like Escherichia coli are subjected to immediate affect of environmental fluctuation that may unfold proteins, due to the permeability of the outer membrane to small molecules. They are thus supposedly protected by certain molecular chaperones. Nevertheless, no homologues of typical molecular chaperones have so far been found in periplasm, and the recently reported chaperone activities of periplasmic protein disulfide isomerase (PDI) and peptidyl prolyl isomerase (PPI) seem to be too weak to satisfy such assumed needs. In an attempt to reveal whether periplasmic proteins exhibit certain unusual properties, we discovered that such proteins as a whole are highly resistant to aggregation under a wide variety of denaturing conditions. Furthermore, in an effort to unveil the nature behind this phenomenon we purified and examined four prominent periplasmic proteins. Our results demonstrate that these proteins unfold at rather mild denaturing conditions and expose hydrophobic surfaces during such unfolding process, but hardly form complexes with a typical molecular chaperone. Based on these observations, we propose that the periplasmic proteins have been evolved to resist the formation of aggregates when subjected to various denaturing conditions and molecular chaperones may thus not be needed in periplasm. 相似文献
993.
The Tibetan Plateau is an essential area to study the potential feedback effects of soils to climate change due to the rapid rise in its air temperature in the past several decades and the large amounts of soil organic carbon (SOC) stocks, particularly in the permafrost. Yet it is one of the most under-investigated regions in soil respiration (Rs) studies. Here, Rs rates were measured at 42 sites in alpine grasslands (including alpine steppes and meadows) along a transect across the Tibetan Plateau during the peak growing season of 2006 and 2007 in order to test whether: (1) belowground biomass (BGB) is most closely related to spatial variation in Rs due to high root biomass density, and (2) soil temperature significantly influences spatial pattern of Rs owing to metabolic limitation from the low temperature in cold, high-altitude ecosystems. The average daily mean Rs of the alpine grasslands at peak growing season was 3.92 μmol CO(2) m(-2) s(-1), ranging from 0.39 to 12.88 μmol CO(2) m(-2) s(-1), with average daily mean Rs of 2.01 and 5.49 μmol CO(2) m(-2) s(-1) for steppes and meadows, respectively. By regression tree analysis, BGB, aboveground biomass (AGB), SOC, soil moisture (SM), and vegetation type were selected out of 15 variables examined, as the factors influencing large-scale variation in Rs. With a structural equation modelling approach, we found only BGB and SM had direct effects on Rs, while other factors indirectly affecting Rs through BGB or SM. Most (80%) of the variation in Rs could be attributed to the difference in BGB among sites. BGB and SM together accounted for the majority (82%) of spatial patterns of Rs. Our results only support the first hypothesis, suggesting that models incorporating BGB and SM can improve Rs estimation at regional scale. 相似文献
994.
欧美杂种山杨体细胞无性系变异的分析 总被引:1,自引:2,他引:1
以成年欧美杂种山杨(Populustremula×P.tremuloides)优良无性系为材料,通过组织培养方法获得体细胞无性系,利用细胞学和分子生物学方法对其发生的变异进行研究。结果表明:用3.0mg.L-12,4-D诱导的再生植株的细胞染色体稳定性较差,所检测的144个细胞中,变异的细胞中多数发生了染色体加倍,二倍体细胞数仅占36.81%。有些染色体还发生了形态变异,染色体加长,形成带有随体或长臂较长的大型染色体。用1.0mg.L-16-BA诱导再生植株中染色体数量稳定性介于对照和3.0mg.L-12,4-D诱导的再生植株之间,在观察的142个细胞中二倍体细胞占54.93%。再生植株的AFLP分析表明,由激素诱导的再生植株中,AFLP谱带发生了变化,表明发生了体细胞无性系分子水平变异。 相似文献
995.
Yang X Zhang Z Jia S Liu Y Wang X Yan Q 《The international journal of biochemistry & cell biology》2007,39(9):1722-1730
Fucosyltransferase IV is an essential enzyme that catalyzes the synthesis of fucosylated oligosaccharides by transferring GDP-fucose to the terminal N-acetylglucosamine with the alpha1,3-linkage. Lewis Y oligosaccharide has a terminal alpha1,3-linked fucose residue and elevation of Lewis Y level is seen in many epithelial cancers. The mechanism of Lewis Y elevation in neoplastic cells is still largely unknown. To study the impact of fucosyltransferase IV on Lewis Y expression and its role on neoplastic cell proliferation, a pEGFP-N1-FUT4 recombinant plasmid was developed and stably transfected into A431 cells. We found that fucosyltransferase IV overexpression promoted cell proliferation and increased the expression of proliferating cell nuclear antigen that correlated with Lewis Y augmentation. Cell cycle analysis demonstrated that fucosyltransferase IV overexpression facilitated cell cycle progression. In conclusion, fucosyltransferase IV overexpression augments Lewis Y expression to trigger neoplastic cell proliferation. These studies suggest that fucosyltransferase IV may serve as a potential therapeutic target for the treatment of Lewis Y-positive epithelial cancers. 相似文献
996.
Jun Feng Weixia Gao Yanyan Gu Wei Zhang Mingfeng Cao Cunjiang Song Peng Zhang Min Sun Chao Yang Shufang Wang 《Applied microbiology and biotechnology》2014,98(14):6397-6407
Poly-γ-glutamic acid (γ-PGA) is an important biopolymer with greatly potential in industrial and medical applications. In the present study, we constructed a metabolically engineered glutamate-independent Bacillus amyloliquefaciens LL3 strain with considerable γ-PGA production, which was carried out by single, double, and triple markerless deletions of three degradation genes pgdS, ggt, and cwlO. The highest γ-PGA production (7.12 g/L) was obtained from the pgdS and cwlO double-deletion strain NK-pc, which was 93 % higher than that of wild-type LL3 strain (3.69 g/L). The triple-gene-deletion strain NK-pgc showed a 28 % decrease in γ-PGA production, leading to a yield of 2.69 g/L. Furthermore, the cell morphologies of the mutant strains were also characterized. The cell length of cwlO deletion strains NK-c and NK-pc was shorter than that of the wild-type strain, while the ggt deletion strains NK-g, NK-pg, NK-gc, and NK-pgc showed longer cell lengths. This is the first report concerning the markerless deletion of γ-PGA degradation genes to improve γ-PGA production in a glutamate-independent strain and the first observation that γ-glutamyltranspeptidase (encoded by ggt) could be involved in the inhibition of cell elongation. 相似文献
997.
Our understanding of the molecular mechanisms of error-prone lesion bypass has changed dramatically in the past few years. The concept that the key participants in the mutagenic process were accessory proteins that somehow modified the ability of the cell's main replicase to facilitate bypass of normally blocking lesions has been replaced with one in which the replicase is displaced by a polymerase specialized in lesion bypass. The participants in this process remain the same, only their function has been reassigned. What was once known as the UmuC/DinB/Rev1/Rad30 superfamily of mutagenesis proteins, is now known as the Y-family of DNA polymerases. Quite remarkably, within the space of 3 years, the field has advanced from the initial discovery of intrinsic polymerase function, to the determination of the tertiary structures of several Y-family DNA polymerases.A key to determining the biochemical properties of each DNA polymerase is through structure-function studies that result in the site-specific substitution of particular amino acids at critical sites within each DNA polymerase. However, we should not forget the power of genetic selection that allows us to identify residues within each polymerase that are generated by "random mutagenesis" and which are important for both a gain or loss of function in vivo. In this review, we discuss the structural ramifications of several missense mutations previously identified in various Y-family DNA polymerase and speculate on how each amino acid substitution might modify the enzymatic activity of the respective polymerase or possibly perturb protein-protein interactions necessary for efficient translesion replication in vivo. 相似文献
998.
Antitumor mechanism of Se-containing polysaccharide, a novel organic selenium compound 总被引:1,自引:0,他引:1
Dejing Shang Qiao Cui Yang Li Zhi Yu Lei Wen Yuan Zhao Jianing Zhang 《Frontiers of Biology in China》2009,4(3):248-253
Recent studies on the inhibition of tumor growth by Se-containing polysaccharide were reviewed. Meanwhile, the possible molecular
mechanisms of the inhibition of tumor cell growth through antioxidation, induction of tumor cell apoptosis, blockade of cell
cycle, and enhancement of immunity by Se-containing polysaccharide were proposed. In the end, the potential application of
Se-containing polysaccharide in the prevention and treatment of tumor was elucidated. 相似文献
999.
Three-dimensional quantitative structure–activity relationship (3D-QSAR) studies were performed on a series of substituted 1,4-dihydroindeno[1,2-c]pyrazoles inhibitors, using molecular docking and comparative molecular field analysis (CoMFA). The docking results from GOLD 3.0.1 provide a reliable conformational alignment scheme for the 3D-QSAR model. Based on the docking conformations and alignments, highly predictive CoMFA model was built with cross-validated q 2 value of 0.534 and non-cross-validated partial least-squares analysis with the optimum components of six showed a conventional r 2 value of 0.911. The predictive ability of this model was validated by the testing set with a conventional r 2 value of 0.812. Based on the docking and CoMFA, we have identified some key features of the 1,4-dihydroindeno[1,2-c]pyrazoles derivatives that are responsible for checkpoint kinase 1 inhibitory activity. The analyses may be used to design more potent 1,4-dihydroindeno[1,2-c]pyrazoles derivatives and predict their activity prior to synthesis. 相似文献
1000.
Xi Lu Xinyi Yang Xue Li Yun Lu Zhitao Ren Longyin Zhao Xinxin Hu Jiandong Jiang Xuefu You 《PloS one》2013,8(7)