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931.
对单核细胞增多性李斯特菌(简称单增李斯特菌)lmo1711基因编码的氨基肽酶进行克隆表达与纯化,并研究该重组蛋白的体外酶学特性。首先通过生物信息学分析预测Lmo1711与氨基肽酶家族成员的亲缘关系及关键活性位点的保守性。利用SWISS-MODEL模拟预测该蛋白的空间结构;构建Lmo1711原核表达载体并转化入E.coli Rosetta中,诱导表达重组目的蛋白,并利用镍离子亲和层析方法纯化目的蛋白;以氨基酸-对硝基苯胺偶联物为底物,Lmo1711通过水解底物N端氨基酸残基产生游离对硝基苯胺单体,405 nm处检测吸光值对该产物进行检测从而分析Lmo1711的酶学特性。在此基础上系统研究Lmo1711对不同氨基酸残基底物的催化特异性,及不同金属离子对该酶活性的影响。经原核表达纯化获得49.3 kDa的重组Lmo1711蛋白,与预测分子量一致;生物信息学分析推测Lmo1711属于M29氨基肽酶家族,且存在保守关键氨基酸活性位点(Glu250、Glu316、His345、Tyr352、His378、Asp380);酶活分析显示,Lmo1711具有较强的氨基肽酶活性,针对不同底物的结合和催化能力差异较大,对亮氨酸残基的亲和程度最高;Lmo1711氨基肽酶活性具有金属离子依赖性,Co~(2+)、Cd~(2+)、Zn~(2+)等多种金属离子均能显著增强其活性,其中Co~(2+)的激活效应最显著。本试验首次发现并证实,单增李斯特菌Lmo1711属于M29氨基肽酶家族成员,具有较强的催化活性,且对金属离子具有不同程度的依赖性。 相似文献
932.
The peregrine falcon (Falco peregrinus) population in southern Scandinavia was almost extinct in the 1970’s. A successful reintroduction project was launched in
1974, using captive breeding birds of northern and southern Scandinavian, Finnish and Scottish origin. We examined the genetic
structure in the pre-bottleneck population using eleven microsatellite markers and compared the data with the previously genotyped
captive breeding population and contemporary wild population. Museum specimens between 53 and 130 years old were analyzed.
Despite an apparent loss of historical genetic diversity, the contemporary population shows a relatively high level of genetic
variation. Considerable gene introgression from captive breeding stock used to repopulate the former range of southern Scandinavian
peregrines may have altered the genetic composition of this population. Both the historical and contemporary northern and
southern Scandinavian populations are genetically differentiated. The reintroduction project implemented in the region and
the use of non-native genetic stock likely prevented the southern Scandinavian population from extinction and thus helped
maintain the level of genetic diversity and prevent inbreeding depression. The population is rapidly increasing in numbers
and range and shows no indication of reduced fitness or adaptive capabilities in the wake of the severe bottleneck and the
reintroduction. 相似文献
933.
934.
Molecular phylogenetic analyses suggest an emerging phylogeny for the extant Placentalia (eutherian) that radically departs
from morphologically based constructions of the past. Placental mammals are partitioned into four supraordinal clades: Afrotheria,
Xenarthra, Laurasiatheria, and Euarchontoglires. Afrotheria form an endemic African clade that includes elephant shrews, golden
moles, tenrecs, aardvarks, hyraxes, elephants, dugongs, and manatees. Datamining databases of genome size (GS) shows that
till today just one afrotherian GS has been evaluated, that of the aardvark Orycteropus afer. We show that the GSs of six selected representatives across the Afrotheria supraordinal group are among the highest for
the extant Placentalia, providing a novel genomic signature of this enigmatic group. The mean GS value of Afrotheria, 5.3
± 0.7 pg, is the highest reported for the extant Placentalia. This should assist in planning new genome sequencing initiatives.
[Reviewing Editor: Dmitri Petrov] 相似文献
935.
Hung-Yen Hsieh Wen-Tseng Lo Don-Chung Liu Pei-Kai Hsu Wei-Cheng Su 《Environmental Biology of Fishes》2007,78(4):333-346
The aim of this study was to investigate the species composition and distribution of fish larvae in relation to hydrographic
conditions in the waters surrounding Taiwan Island (TI) in February 2003. In total, 242 kinds of fish larvae belonging to
127 genera and 75 families were recognized. Among these, 109 taxa were identified to the family or genus level, others to
the species level. The 12 predominant types, which constituted 71% of the total fish larvae, were Engraulis japonica, Scomber sp., Diaphus spp., Benthosema pterotum, Carangoides ferdau, Embolichthys mitsukurii, Maurolicus sp., unidentified Myctophidae, Gonostoma gracile, Trichiurus lepturus, unidentified Gobiidae, and Myctophum asperum. The distribution of fish larvae showed a clear association with water masses around TI, with higher abundances and lower
species richness northwest of TI where the China Coastal Current prevails, and lower abundances and higher species diversity
east of TI where the Kuroshio Current dominates. Cluster analysis distinguished three station groups and four species groups,
and the distribution patterns of fish larvae also corresponded to hydrographic conditions. The total abundances of fish larvae
and eight of the 12 predominant taxa showed significant and positive correlations with zooplankton abundance, which suggests
that food source might be a key factor determining the abundance and distribution of fish larvae during the winter. 相似文献
936.
Suk Hee Lee Suk Oh Young Il Kim Sang Cheol Jun Sang Sup So Hwan Gyu Kim 《Biotechnology and Bioprocess Engineering》2007,12(2):100-105
Phellinus linteus is a fungus which is found primarily in tropical regions of the Americas, Africa, and Asia.P. linteus has been used in traditional medical practice for the treatment of arthritis, liver damage and cancer. Angiogenesis is a
process that involves migration, proliferation and cell differentiation, as well as the formation of new capillary structures.
The anti-angiogenic activities evidenced by natural compounds may actually be a critical effect for the inhibition of angiogenesis-dependent
disease by these agents via the blockage of vascular development. This study assessed the effects of water extracts fromP. linteus (Phellinus extracts) on primary cultured porcine coronary artery endothelial cells (PCAECs).Phellinus extracts induced no changes in DNA synthesis or cell numbers, but inhibited the migration of PCAECs.Phellinus extracts also induced a reduction in the secretion of matrix metalloproteinase-2 (MMP-2) and MMP-9. Our results show that,
in endothelial cells,Phellinus extracts may inhibit angiogenesis by reducing levels of MMP-2 and MMP-9 secretion. 相似文献
937.
Zhang Y Yang F Kao YC Kurilla MG Pompliano DL Dicker IB 《Analytical biochemistry》2002,304(2):174-179
Escherichia coli DnaG primase is a single-stranded DNA-dependent RNA polymerase. Primase catalyzes the synthesis of a short RNA primer to initiate DNA replication at the origin and to initiate Okazaki fragment synthesis for synthesis of the lagging strand. Primase activity is greatly stimulated through its interaction with DnaB helicase. Here we report a 96-well homogeneous scintillation proximity assay (SPA) for the study of DnaB-stimulated E. coli primase activity and the identification of E. coli primase inhibitors. The assay uses an adaptation of the general priming reaction by employing DnaG primase, DnaB helicase, and ribonucleotidetriphosphates (incorporation of [(3)H]CTP) for in vitro primer synthesis on single-stranded oligonucleotide and M13mp18 DNA templates. The primase product is captured by polyvinyl toluene-polyethyleneimine-coated SPA beads and quantified by counting by beta-scintography. In the absence of helicase as a cofactor, primer synthesis is reduced by 85%. The primase assay was used for screening libraries of compounds previously identified as possessing antimicrobial activities. Primase inhibitory compounds were then classified as direct primase inhibitors or mixed primase/helicase inhibitors by further evaluation in a specific assay for DnaB helicase activity. By this approach, specific primase inhibitors could be identified. 相似文献
938.
目的:探讨IKK激酶催化亚基IKKα在分别介导生长促进信号(血清)和生长抑制信号(紫外线UVB)诱导的反应中,调控转录因子AP-1关键组成亚基c-Fos实现诱导表达的信号传递机制。方法:分别采用Western印迹、RT-PCR和萤光素酶报道分析系统检测血清和紫外线刺激反应状态下IKKα对c-Fos诱导表达和AP-1诱导活化的调控作用;通过转染I-κBα功能抑制型突变体I-κBα-AA,观察NF-κB诱导活化受抑时,c-Fos诱导表达和AP-1诱导活化水平的改变情况。结果:IKKα在生长促进和生长抑制信号诱导的反应中,都能够实现对转录因子AP-1及其关键组成亚基c-Fos诱导表达的调控作用。其中,在血清反应中IKKα可通过NF-κB依赖方式在转录水平调控c-Fos的诱导表达,而在UVB反应中IKKα通过转录非依赖方式调控c-Fos的诱导表达。结论:IKKα能分别以NF-κB依赖和非依赖方式参与调控生长促进和生长抑制信号诱导的反应。 相似文献
939.
Recovery of transgenic plants by pollen-mediated transformation in <Emphasis Type="Italic">Brassica juncea</Emphasis> 总被引:1,自引:0,他引:1
The aroA-M1 encoding the mutant of 5-enolpyruvyl-shikimate-3-phosphate synthase (EPSPS) was introduced into the Brassica juncea genome by sonication-assisted, pollen-mediated transformation. The plasmid DNA and collected pollen grains were mixed in
0.3 mol/L sucrose solution and treated with mild ultrasonication. The treated pollen was then pollinated onto the oilseed
stigmas after the stamens were removed artificially. Putative transgenic plants were obtained by screening germinating seeds
on a medium containing glyphosate. Southern blot analysis of glyphosate-resistant plants indicated that the aroA-M1 gene had been integrated into the oilseed genome. Western blot analysis further confirmed that the EPSPS coded by aroA-M1 gene was expressed in transgenic plants. The transgenic plants exhibited increased resistance to glyphosate compared to untransformed
plants. Some of those transgenic plants had considerably high resistance to glyphosate. The genetic analysis of T1 progeny further confirmed that the inheritance of the introduced genes followed the Mendelian rules. The results indicated
that foreign genes can be transferred by pollen-mediated transformation combined with mild ultrasonication. 相似文献
940.
A thermophilic bacterial strain GXN151 which could degrade Avicel efficiently was isolated and identified as Bacillus licheniformis. A genomic library of GXN151 was constructed and two novel endoglucanase genes designated cel9A and cel12A were isolated by screening the library on carboxylmethyl cellulase indicator plates. The analysis of amino acid sequences deduced from the genes indicated that Cel9A consisted of a catalytic domain belonging to glycosyl hydrolase family 9, a linker domain, and a carbohydrate binding module family 3 from N-terminal to C-terminal; Cel12A had only one catalytic domain belonging to glycosyl hydrolase family 12. The combinations of Cel9A and Cel12A produced by the recombinant E. coli exhibited synergistic action against substrates of carboxylmethyl cellulose as well as Avicel. 相似文献