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951.
The melibiose permease of Salmonella enterica serovar Typhimurium (MelBSt) catalyzes symport of melibiose with Na+, Li+, or H+. Bioinformatics and mutational analyses indicate that a conserved Gly117 (helix IV) is a component of the Na+-binding site. In this study, Gly117 was mutated to Ser, Asn, or Cys. All three mutations increase the maximum rate (Vmax) for melibiose transport in Escherichia coli DW2 and greatly decrease Na+ affinity, indicating that intracellular release of Na+ is facilitated. Rapid melibiose transport, particularly by the G117N mutant, triggers osmotic lysis in the lag phase of growth. The findings support the previous conclusion that Gly117 plays an important role in cation binding and translocation. Furthermore, a spontaneous second-site mutation (P148L between loop4-5 and helix V) in the G117C mutant prevents cell lysis. This mutation significantly decreases Vmax with little effect on cosubstrate binding in G117C, G117S, and G117N mutants. Thus, the P148L mutation specifically inhibits transport velocity and thereby blocks the lethal effect of elevated melibiose transport in the Gly117 mutants. 相似文献
952.
953.
Hu W Onuma T Birukawa N Abe M Ito E Chen Z Urano A 《Cellular and molecular neurobiology》2008,28(4):519-528
Elevation of the intracellular cAMP level induces morphological changes of astrocyte-like differentiation in C6 glioma cells.
Such changes may be accompanied with expression of cytoskeletal protein genes. We therefore analyzed morphological changes
after a treatment with dibutyryl cAMP (dbcAMP) and then assessed the expression of cytoskeletal protein genes by a quantitative
real-time polymerase chain reaction. The cell number remained unaltered upon incubation with 1 mM dbcAMP in medium supplemented
with 0.1% fetal bovine serum (FBS), whereas the number and lengths of processes increased, when compared with those of cells
incubated in medium supplemented with 0.1% or 10% FBS only. The amounts of β-actin, γ-actin, and β-tubulin mRNAs in C6 cells,
but not α-tubulin mRNA, increased during the early proliferation in DMEM containing 10% FBS. The expression of cytoskeletal
protein genes decreased when incubated with 0.1% FBS or 1 mM dbcAMP in 0.1% FBS, compared with those of cells cultured in
10% FBS. These results indicated that, during the early proliferation in normal culture condition, the expression of cytoskeletal
protein genes in C6 cells, except α-tubulin, increased, while in differentiating or differentiated C6 glioma cells, cAMP-induced
morphological changes were not accompanied with elevation of gene expression for cytoskeletal proteins, such as actin and
tubulin. 相似文献
954.
955.
Peptidoglycan recognition proteins of the innate immune system 总被引:1,自引:0,他引:1
Peptidoglycan (PGN) is the major component of bacterial cell walls and one of the main microbial products recognized by the innate immune system. PGN recognition is mediated by several families of pattern recognition molecules, including Toll-like receptors, nucleotide-binding oligomerization domain-containing proteins, and peptidoglycan recognition proteins (PGRPs). However, only the interaction of PGN with PGRPs, which are highly conserved from insects to mammals, has so far been characterized at the molecular level. Here, we describe recent structural studies of PGRPs that reveal the basis for PGN recognition and provide insights into the signal transduction and antibacterial activities of these innate immune proteins. 相似文献
956.
Grzegorz Nalepa Jill Barnholtz-Sloan Rikki Enzor Dilip Dey Ying He Jeff R. Gehlhausen Amalia S. Lehmann Su-Jung Park Yanzhu Yang Xianlin Yang Shi Chen Xiaowei Guan Yanwen Chen Jamie Renbarger Feng-Chun Yang Luis F. Parada Wade Clapp 《The Journal of cell biology》2013,201(7):997-1012
Mitosis is controlled by a network of kinases and phosphatases. We screened a library of small interfering RNAs against a genome-wide set of phosphatases to comprehensively evaluate the role of human phosphatases in mitosis. We found four candidate spindle checkpoint phosphatases, including the tumor suppressor CDKN3. We show that CDKN3 is essential for normal mitosis and G1/S transition. We demonstrate that subcellular localization of CDKN3 changes throughout the cell cycle. We show that CDKN3 dephosphorylates threonine-161 of CDC2 during mitotic exit and we visualize CDC2pThr-161 at kinetochores and centrosomes in early mitosis. We performed a phosphokinome-wide mass spectrometry screen to find effectors of the CDKN3-CDC2 signaling axis. We found that one of the identified downstream phosphotargets, CKβ phosphorylated at serine 209, localizes to mitotic centrosomes and controls the spindle checkpoint. Finally, we show that CDKN3 protein is down-regulated in brain tumors. Our findings indicate that CDKN3 controls mitosis through the CDC2 signaling axis. These results have implications for targeted anticancer therapeutics. 相似文献
957.
Siming Wei Bin Yong Hongwei Jiang Zhenghong An Yan Wang Bingbing Li Ce Yang Weiwei Zhu Qingshan Chen Chaoying He 《植物学报(英文版)》2023,65(11):2469-2489
The resultant DNA from loss-of-function mutation can be recruited in biological evolution and development. Here, we present such a rare and potential case of “to gain by loss” as a neomorphic mutation during soybean domestication for increasing seed weight. Using a population derived from a chromosome segment substitution line of Glycine max(SN14) and Glycine soja(ZYD06), a quantitative trait locus(QTL) of 100-seed weight(q HSW) was mapped on chromosome 11, corresponding to a truncated β-1, 3-gl... 相似文献
958.
Fu J Yamamoto K Guan ZW Kimura S Iyanagi T 《Archives of biochemistry and biophysics》2004,427(2):180-187
We have analyzed the mechanism of one-electron reduction of adriamycin (Adr) using recombinant full-length human neuronal nitric-oxide synthase and its flavin domains. Both enzymes catalyzed aerobic NADPH oxidation in the presence of Adr. Calcium/calmodulin (Ca(2+)/CaM) stimulated the NADPH oxidation of Adr. In the presence or absence of Ca(2+)/CaM, the flavin semiquinone radical species were major intermediates observed during the oxidation of the reduced enzyme by Adr. The FAD-NADPH binding domain did not significantly catalyze the reduction of Adr. Neither the FAD semiquinone (FADH*) nor the air-stable semiquinone (FAD-FMNH*) reacted rapidly with Adr. These data indicate that the fully reduced species of FMN (FMNH(2)) donates one electron to Adr, and that the rate of Adr reduction is stimulated by a rapid electron exchange between the two flavins in the presence of Ca(2+)/CaM. Based on these findings, we propose a role for the FAD-FMN pair in the one-electron reduction of Adr. 相似文献
959.
960.
大豆不同生育期根际土壤细菌群落结构的变化 总被引:2,自引:0,他引:2
为了解大豆根际细菌群落结构多样性及根际细菌群落结构的变化,该研究以大豆苗期和成熟期的根际土壤为材料,采用Illumina高通量测序技术测定细菌16S rRNA V3+V4区序列,探究大豆不同生育期根际土壤细菌群落结构的变化。对原始数据进行拼接、过滤、去除嵌合体序列和聚类分析等数据处理,并对OTU进行分类学注释。在此基础上运用ANOVA分析物种组成变化,Alpha多样性指数研究细菌多样性变化。结果表明:细菌丰富度和多样性在不同生育期有显著变化,其中成熟期土壤中的细菌丰富度和多样性指数均明显高于苗期; 变形菌、放线菌、酸杆菌是大豆根际的优势菌门,其含量在不同生育期也有显著变化; 假诺卡氏菌属、糖丝菌属、鞘氨醇单胞菌属是大豆根际的优势菌属,这些菌属中的部分菌群属于根际促生菌,具有潜在的促生效应。这些结果证实大豆的生育期对根际土壤细菌群落结构有重要影响。 相似文献