Structure of the Methanococcus jannaschii mevalonate kinase, a member of the GHMP kinase superfamily.

The mevalonate-dependent pathway is used by many organisms to synthesize isopentenyl pyrophosphate, the building block for the biosynthesis of many biologically important compounds, including farnesyl pyrophosphate, dolichol, and many sterols. Mevalonate kinase (MVK) catalyzes a critical phosphoryl transfer step, producing mevalonate 5'-phosphate. The crystal structure of thermostable MVK from Methanococcus jannaschii has been determined at 2.4 A, revealing an overall fold similar to the homoserine kinase from M. jannaschii. In addition, the enzyme shows structural similarity with mevalonate 5-diphosphate decarboxylase and domain IV of elongation factor G. The active site of MVK is in the cleft between its N- and C-terminal domains. Several structural motifs conserved among species, including a phosphate-binding loop, have been found in this cavity. Asp(155), an invariant residue among MVK sequences, is located close to the putative phosphate-binding site and has been assumed to play the catalytic role. Analysis of the MVK model in the context of the other members of the GHMP kinase family offers the opportunity to understand both the mechanism of these enzymes and the structural details that may lead to the design of novel drugs.     

Regulation of human immunodeficiency virus type 1 infectivity by the ERK mitogen-activated protein kinase signaling pathway

ERK1 and ERK2 mitogen-activated protein kinases (MAPK) play a critical role in regulation of cell proliferation and differentiation in response to mitogens and other extracellular stimuli. Mitogens and cytokines that activate MAPK in T cells have been shown to activate human immunodeficiency virus type 1 (HIV-1) replication. Little is known about the signal transduction pathways that activate HIV-1 replication in T cells upon activation by extracellular stimulation. Here, we report that activation of MAPK through the Ras/Raf/MEK signaling pathway enhances the infectivity of HIV-1 virions. Virus infectivity was enhanced by treatment of cells with MAPK stimulators, such as serum and phorbol myristate acetate, as well as by coexpression of constitutively activated Ras, Raf, or MEK (MAPK kinase) in the absence of extracellular stimulation. Treatment of cells with PD 098059, a specific inhibitor of MAPK activation, or with a MAPK antisense oligonucleotide reduced the infectivity of HIV-1 virions without significantly affecting virus production or the levels of virion-associated Gag and Env proteins. MAPK has been shown to regulate HIV-1 infectivity by phosphorylating Vif (X. Yang and D. Gabuzda, J. Biol. Chem. 273:29879-29887, 1998). However, MAPK activation enhanced virus infectivity in some cells lines that do not require Vif function. The HIV-1 Rev, Tat, p17(Gag), and Nef proteins were directly phosphorylated by MAPK in vitro, suggesting that other HIV-1 proteins are potential substrates for MAPK phosphorylation. These results suggest that activation of the ERK MAPK pathway plays a role in HIV-1 replication by enhancing the infectivity of HIV-1 virions through Vif-dependent as well as Vif-independent mechanisms. MAPK activation in producer cells may contribute to the activation of HIV-1 replication when T cells are activated by mitogens and other extracellular stimuli.     

温度和光周期对烟蚜性蚜的诱导

本文研究了温度和光周期对烟蚜性蚜诱导的影响,结果表明：郑州地区的红色和黄绿色烟蚜在１０小时光照和１５、２０℃组合下可产生性雌和雄蚜,而在１２、１４和８小时及２５℃条件下均未有性蚜产生。     

难培养菌的多条带PCR产物产生原因分析

【目的】分析严重威胁柑橘产业发展的毁灭性病害——柑橘黄龙病的强致病性病原亚洲种“Candidatus Liberibacter asiaticus”的种群多样性研究中出现多条带PCR产物的原因,为难培养菌的分子生物学研究提供参考。【方法】通过使用PCR、聚丙烯酰胺凝胶电泳(PAGE)和测序相结合分析“Ca. L. asiaticus”基因组上2个短串联重复(Short tandem repeats,STR)基因的PCR产物。【结果】单个菌株可扩增获得多个PCR条带且其扩增产物多态性受寄主品种影响;这2个STR基因的PCR产物在菌株间呈明显的多态性;扩增所获得的序列可来自“Ca. L. asiaticus”本身,也可来自其寄主或内生菌。【结论】难培养菌的STR基因PCR产物多态性产生的主要原因是该基因内部的串联重复序列数目存在差异,但目的菌及外源物种(寄主或内生菌等)基因组的非特异性扩增也是影响其多态性的因素。     

T-piece复苏器在产房中对早产儿复苏中的应用效果评价*

目的:探讨T-piece复苏器在产房中对早产儿复苏中的应用效果。方法:选择2011年1月至2016年12月在本院产科出生的早产儿(胎龄28～37周)62例,随机分为对照组与观察组,各31例,对照组患儿给予自动充气式复苏囊正压人工通气,观察组患儿给予T组合复苏器正压人工通气,比较两组患儿1、5、10 min Apgar评分、肺气漏发生率,以及缺氧缺血性脑病、支气管肺发育不良、坏死性小肠结肠炎、动脉导管未闭、高胆红素血症率。结果:两组患儿胎龄、性别、分娩方式、出生体重、出生后1、5、10 min Apgar评分等方面差异均无统计学意义(P0.05)。与对照组相比,观察组气漏发生率降低,差异有统计学意义(P0.05)。两组患儿缺氧缺血性脑病、支气管肺发育不良、坏死性小肠结肠炎、动脉导管未闭、高胆红素血症率差异无统计学意义(P0.05)。结论:T-piece复苏器在产房中早产儿窒息复苏中的应用效果显著,具有操作简单、效率高等优点,两组复苏成功率差别不大,但T-piece复苏器能可有效减少肺气漏的发生,进而降低新生儿的病死率。     

海南岛翼手目物种多样性现状与分布预测

海南岛位于我国南部, 地处热带北缘, 其独特的岛屿气候环境孕育了丰富的生物资源, 为我国生物多样性热点地区之一。为探究岛内的翼手目物种多样性状况, 本研究组使用雾网、蝙蝠竖琴网等工具, 于2002年至2016年先后对海南岛进行了15次翼手目多样性调查, 并根据其外形与头骨特征及系统发育学方法进行标本鉴定。共获取了1,025号标本, 隶属5科15属31种, 其中2016年12月21日在海南琼中捕获的艾氏管鼻蝠(Murina eleryi)为海南岛蝙蝠分布新记录。结合前人调查及发表结果统计, 岛内共有翼手类8科20属41种。同时基于本调查采集位点和前人调查位置信息(共计363个位点), 结合WorldClim 32种气候数据, 运用最大熵模型(MaxEnt)对海南岛翼手目物种的分布进行预测, 结果显示五指山、吊罗山、鹦哥岭、尖峰岭及海口火山口国家地质公园等地为翼手目物种多样性较丰富的区域, 而三亚、澄迈、屯昌、临高、琼海等地翼手目物种多样性较低。本研究结果为海南岛翼手目资源分布及多样性状况提供了基础资料, 也为岛内后续开展翼手目资源保护管理、蝙蝠疾病防控等提供了重要的参考依据。     

微生态制剂对海水养殖系统硝化功能建立过程的影响

比较分析投加不同微生态制剂的海水养殖系统硝化功能建立的过程,为实际应用提供依据。利用海水素构建4个海水养殖系统,通过投加硝化细菌、光合细菌、枯草芽胞杆菌3种微生态制剂以及纤维毛球作为生物膜载体,比较分析不同养殖系统硝化功能的建立过程及硝化强度差异。投加硝化细菌+光合细菌和硝化细菌+枯草芽胞杆菌系统硝化功能建立时间分别为108 h和96 h,氨氮初始质量浓度为6 mg/L时,氨氧化强度分别为1.69 mg/(L·d)和1.36 mg/(L·d);添加纤维毛球的生物膜系统与生物絮团系统硝化功能建立时间分别为96 h和120 h,氨氮初始质量浓度为6 mg/L时,氨氧化强度分别为1.36 mg/(L·d)和0.98 mg/(L·d);投加碳源系统和对照系统硝化功能建立时间分别为84 h和96 h,氨氮初始质量浓度为6 mg/L时,氨氧化强度分别为1.18 mg/(L·d)和1.36 mg/(L·d)。硝化细菌+枯草芽胞杆菌系统硝化功能建立时间更短,但系统硝化强度低于硝化细菌+光合细菌系统;生物膜系统硝化强度高于生物絮团系统且硝化功能建立更快;添加碳源能够加快系统硝化功能建立过程,但降低了硝化细菌+枯草芽胞杆菌系统的硝化强度。     

Aureonitols A and B,Two New C13‐Polyketides from Chaetomium globosum,an Endophytic Fungus in Salvia miltiorrhiza

Two new C₁₃‐polyketides, aureonitols A and B ( 1 and 2 ), along with five known compounds ( 3 – 7 ), were isolated from the solid fermentation culture of the plant endophytic fungus Chaetomium globosum from the aerial parts of Salvia miltiorrhiza. The structures and absolute configurations of 1 and 2 were determined by comprehensive spectroscopic data analysis and computed methods. Compound 5 was found to display the remarkable antimicrobial activities against four multidrug‐resistant bacteria (Enterococcus faecalis, Enterococcus faecium, Staphylococcus aureus, and Staphylococcus epidermidis) with MIC values of 3.13–6.25 μg/mL (ciprofloxacin: 0.78–1.56 μg/mL), and also against all tested fungal strains with MIC values of 3.13–25 μg/mL (ketoconazole: 0.78–12.50 μg/mL).     

Mating system shifts a species’ range

Understanding the ecological and evolutionary mechanisms that shape a species’ range is an important goal in evolutionary biology. Evidence indicates that mating system is an effective predictor of the global range of native species or naturalized alien plants, but the mechanisms underlying this predictability are not elaborated. Here, we develop a theoretical model to account for the ranges of plants under different mating systems based on migration‐selection processes (an idea proposed by Haldane). The model includes alternation of gametophyte and sporophyte generations in one life cycle and the dispersal of haploid pollen and diploid seeds as vectors for gene flow. We show that the interaction between selfing rates and gametophytic selection determines the role of mating system in shaping a species’ range. Selfing restricts the species’ range under gametophytic selection in nonrandom mating systems, but expands the species’ range under the absence of gametophytic selection in any mating system. Gametophytic selection slightly restricts the species’ range in random mating. Both logarithmic and logistic models of population demography yield similar conclusions in the case of fixed or evolving genetic variance. The theory also helps to explain a broader relationship between mating system and range size following biological invasion or plant naturalization.