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961.
Tai‐Wen Lin Chi‐Chih Chen Shu‐Mei Wu Yu‐Ching Chang Yi‐Chuan Li Yu‐Wang Su Chwan‐Deng Hsiao Hsin‐Yang Chang 《The Plant journal : for cell and molecular biology》2019,99(1):128-143
In mammals and yeast, tail‐anchored (TA) membrane proteins destined for the post‐translational pathway are safely delivered to the endoplasmic reticulum (ER) membrane by a well‐known targeting factor, TRC40/Get3. In contrast, the underlying mechanism for translocation of TA proteins in plants remains obscure. How this unique eukaryotic membrane‐trafficking system correctly distinguishes different subsets of TA proteins destined for various organelles, including mitochondria, chloroplasts and the ER, is a key question of long standing. Here, we present crystal structures of algal ArsA1 (the Get3 homolog) in a distinct nucleotide‐free open state and bound to adenylyl‐imidodiphosphate. This approximately 80‐kDa protein possesses a monomeric architecture, with two ATPase domains in a single polypeptide chain. It is capable of binding chloroplast (TOC34 and TOC159) and mitochondrial (TOM7) TA proteins based on features of its transmembrane domain as well as the regions immediately before and after the transmembrane domain. Several helices located above the TA‐binding groove comprise the interlocking hook‐like motif implicated by mutational analyses in TA substrate recognition. Our data provide insights into the molecular basis of the highly specific selectivity of interactions of algal ArsA1 with the correct sets of TA substrates before membrane targeting in plant cells. 相似文献
962.
Songtao Li Hongling Zhao Xiaomin Chang Jianping Wang Enhong Zhao Zhifeng Yin Xiaoxia Mao Shuhua Deng Ting Hao Huina Wang Yaqi Yang 《Journal of peptide science》2019,25(1)
Overexpression of gonadotropin‐releasing hormone (GnRH) receptor in many tumors but not in normal tissues makes it possible to use GnRH analogs as targeting peptides for selective delivery of cytotoxic agents, which may help to enhance the uptake of anticancer drugs by cancer cells and reduce toxicity to normal cells. The GnRH analogs [d ‐Cys6, desGly10, Pro9‐NH2]‐GnRH, [d ‐Cys6, desGly10, Pro9‐NHEt]‐GnRH, and [d ‐Cys6, α‐aza‐Gly10‐NH2]‐GnRH were conjugated with doxorubicin (Dox), respectively, through N‐succinimidyl‐3‐maleimidopropionate as a linker to afford three new GnRH‐Dox conjugates. The metabolic stability of these conjugates in human serum was determined by RP‐HPLC. The antiproliferative activity of the conjugates was examined in GnRH receptor‐positive MCF‐7 human breast cancer cell line by MTT assay. The three GnRH‐Dox conjugates showed improved metabolic stability in human serum in comparison with AN‐152. The antiproliferative effect of conjugate II ([d ‐Cys6, desGly10, Pro9‐NHEt]‐GnRH‐Dox) on MCF‐7 cells was higher than that of conjugate I ([d ‐Cys6, desGly10, Pro9‐NH2]‐GnRH‐Dox) and conjugate III ([d ‐Cys6, α‐aza‐Gly10‐NH2]‐GnRH‐Dox), and the cytotoxicity of conjugate II against GnRH receptor‐negative 3T3 mouse embryo fibroblast cells was decreased in comparison with free Dox. GnRH receptor inhibition test suggested that the antiproliferative activity of conjugate II might be due to the cellular uptake mediated by the targeting binding of [d ‐Cys6‐des‐Gly10‐Pro9‐NHEt]‐GnRH to GnRH receptors. Our study indicates that targeting delivery of conjugate II mediated by [d ‐Cys6‐des‐Gly10‐Pro9‐NHEt]‐GnRH is a promising strategy for chemotherapy of tumors that overexpress GnRH receptors. 相似文献
963.
964.
Shih‐Fan Chan Wei‐Kai Shih An‐Yu Chang Sheng‐Feng Shen I‐Ching Chen 《Ecology letters》2019,22(10):1668-1679
How abiotic and biotic factors constrain distribution limits at the harsh and benign edges of species ranges is hotly debated, partly because macroecological experiments testing the proximate causes of distribution limits are scarce. It has long been recognized – at least since Darwin’s On the Origin of Species – that a harsh climate strengthens competition and thus sets species range limits. Using thorough field manipulations along a large elevation gradient, we show the mechanisms by which temperature determines competition type, resulting in a transition from interference to exploitative competition from the lower to the upper elevation limits in burying beetles (Nicrophorus nepalensis). This transition is an example of Darwin’s classic hypothesis that benign climates favor direct competition for highly accessible resources while harsh climates result in competition through resources of high rivalry. We propose that identifying the properties of these key resources will provide a more predictive framework to understand the interplay between biotic and abiotic factors in determining geographic range limits. 相似文献
965.
Qiang Zheng Qi Chen Ruanhong Cai Chen He Weidong Guo Yu Wang Quan Shi Chang Chen Nianzhi Jiao 《Environmental microbiology》2019,21(7):2533-2543
In this study, we investigated the microbially mediated transformation of labile Synechococcus-derived DOM to RDOM using a 60-day experimental incubation system. Three phases of TOC degradation activity (I, II and III) were observed following the addition of Synechococcus-derived DOM. The phases were characterized by organic carbon consumption rates of 8.77, 1.26 and 0.16 μmol L−1 day−1, respectively. Excitation emission matrix analysis revealed the presence of three FDOM components including tyrosine-like, fulvic acid-like, and humic-like molecules. The three components also exhibited differing biological availabilities that could be considered as labile DOM (LDOM), semi-labile DOM (SLDOM) and RDOM, respectively. DOM molecular composition was also evaluated using FT-ICR MS. Based on differing biological turnover rates and normalized intensity values, a total of 1704 formulas were identified as candidate LDOM, SLDOM and RDOM molecules. Microbial transformation of LDOM to RDOM tended to proceed from high to low molecular weight, as well as from molecules with high to low double bond equivalent (DBE) values. Relatively higher aromaticity was observed in the formulas of RDOM molecules relative to those of LDOM molecules. FDOM components provide valuable proxy information to investigate variation in the bioavailability of DOM. These results suggest that coordinating fluorescence spectroscopy and FT-ICR MS of DOM, as conducted here, is an effective strategy to identify and characterize LDOM, SLDOM and RDOM molecules in incubation experiments emulating natural systems. The results described here provide greater insight into the metabolism of phytoplankton photosynthate by heterotrophic bacteria in marine environments. 相似文献
966.
Dam Go Junghwan Lee Ji‐Ae Choi Soo‐Na Cho Seon‐Hwa Kim Sang‐Hun Son Chang‐Hwa Song 《Cellular microbiology》2019,21(12)
Mycobacterium avium, a slow‐growing nontuberculous mycobacterium, causes fever, diarrhoea, loss of appetite, and weight loss in immunocompromised people. We have proposed that endoplasmic reticulum (ER) stress‐mediated apoptosis plays a critical role in removing intracellular mycobacteria. In the present study, we investigated the role of the regulated IRE1‐dependent decay (RIDD) pathway in macrophages during M. avium infection based on its role in the regulation of gene expression. The inositol‐requiring enzyme 1 (IRE1)/apoptosis signal‐regulating kinase 1 (ASK1)/c‐Jun N‐terminal kinase (JNK) signalling pathway was activated in macrophages after infection with M. avium. The expression of RIDD‐associated genes, such as Bloc1s1 and St3gal5, was decreased in M. avium‐infected macrophages. Interestingly, M. avium‐induced apoptosis was significantly suppressed by pretreatment with irestatin (inhibitor of IRE1α) and 4μ8c (RIDD blocker). Macrophages pretreated with N‐acetyl cysteine (NAC) showed decreased levels of reactive oxygen species (ROS), IRE1α, and apoptosis after M. avium infection. The expression of Bloc1s1 and St3gal5 was increased in NAC‐pretreated macrophages following infection with M. avium. Growth of M. avium was significantly increased in irestatin‐, 4μ8c‐, and NAC‐treated macrophages compared with the control. The data indicate that the ROS‐mediated ER stress response induces apoptosis of M. avium‐infected macrophages by activating IRE1α‐RIDD. Thus, activation of IRE1α suppresses the intracellular survival of M. avium in macrophages. 相似文献
967.
968.
比较广西北部湾石莼(Ulva lactuca L.)、海带(Laminaria japonica)、裙带菜(Undaria pinnatifida Surin-gar)、紫菜(Porphyra)的单糖组成及抗氧化活性的差异,揭示多糖结构与其体外抗氧化活性的关系。利用PMP柱前衍生化HPLC分析海藻多糖的单糖组成,采用羟自由基清除试验、超氧阴离子自由基清除试验及DPPH自由基清除试验指征其体外抗氧化活性,结果表明,4种海藻多糖的单糖组成在主成分空间分布离散,石莼及紫菜主要由葡萄糖组成,海带主要由甘露糖组成,裙带菜则主要由半乳糖组成;其体外抗氧化活性存在显著差异,裙带菜多糖对DPPH的清除能力(半抑制浓度IC50值为0. 56±0. 02 mg/mL)显著高于其他3种海藻多糖;石莼、裙带菜与海带对羟自由基均有较强的清除活性,而紫菜多糖对羟自由基的清除能力较差(IC50值为26. 59±0. 98mg/mL);石莼与裙带菜对超氧阴离子的清除活性较强,显著高于海带与紫菜,其中石莼显著高于裙带菜,IC50值分别为1. 61±0. 17、2. 73±0. 06 mg/mL。相关性分析及冗余分析结果表明,对抗氧化活性影响较为显著的因子为葡萄糖(Glc)、核糖(Rib)、木糖(Xyl)(P <0. 01)。 相似文献
969.
Huanhuan Chen Lei Zhang Zhenqiang Wang Haoya Chang Xiaogang Xie Liangzheng Fu Yong Zhang Fusheng Quan 《Molecular reproduction and development》2019,86(7):862-870
Resveratrol (Res) has been reported to be able to improve oocyte vitrification because of its antioxidative properties. The objective of this study was to further assess the positive effect of Res addition on the developmental potential of vitrified mouse oocytes from the perspective of epigenetic alterations. First, 2 μM Res was chosen as the optimal concentration on the basis of its effects on survival and its antioxidative properties. We found that Res addition significantly promoted fertilization (63.8% vs. 42.9%) and blastocyst formation (68.3% vs. 50.2%) after oocyte vitrification. The quality of the derived blastocysts was also higher after Res treatment. Regarding epigenetic aspects, the expression of the important deacetylase SIRT1 was found to decrease significantly upon vitrification, but it was rescued by Res. The abnormal levels of H3K9 acetylation and DNA methylation in vitrified oocytes were restored by Res addition. Moreover, the expression of several imprinted genes was affected by oocyte vitrification. Among them, abnormal Gtl2 and Peg3 expression levels were restored by Res addition. Therefore, the methylation of their imprinted control regions (ICRs) was examined. Surprisingly, the abnormal patterns of Gtl2 and Peg3 methylation in blastocysts developed from vitrified oocytes were both restored by Res addition. Finally, the full‐term embryonic development showed that the birth rate was improved significantly by Res addition (56.2% vs. 38.1%). Collectively, Res was beneficial for the pre‐ and postimplantation embryonic development. Except for the antioxidative activity, Res also played a role in the correction of some abnormal epigenetic modifications caused by oocyte vitrification. 相似文献
970.
Hyunsoo Kang Byeonghyeok Park Nicole R. Bolo Duleepa Pathiraja Shinyoung Park Minseok Cha In‐G. Choi In S. Chang 《Biotechnology journal》2019,14(6)
Syngas fermentation is largely dependent on acetogens that occur in various anaerobic environmental samples including soil, sediment, and feces. Here the authors report the metagenomic isolation of acetogens for C2 chemical production from syngas. Screening acetogens for C2 chemical production typically involves detecting the presence of the Wood‐Ljungdahl Pathway for carbon monoxide conversion. The authors collect samples from river‐bed sediments potentially having conditions suitable for carbon monoxide‐converting anaerobes, and enrich the samples under carbon monoxide selection pressure. Changes in the microbial community during the experimental procedure are investigated using both amplicon and shotgun metagenome sequencing. Combined next‐generation sequencing techniques enabl in situ tracking of the major acetogenic bacterial group and lead to the discovery of a 16 kb of gene cluster for WLP. The authors isolat an acetogenic clostridial strain from the enrichment culture (strain H21‐9). The functional activity of H21‐9 is confirmed by its high level of production of C2 chemicals from carbon monoxide (77.4 mM acetate and 2.5 mM of ethanol). This approach of incorporating experimental enrichment with metagenomic analysis can facilitate the discovery of novel strains from environmental habitats by tracking target strains during the screening process, combined with validation of their functional activity. 相似文献