共查询到20条相似文献,搜索用时 46 毫秒
1.
构建了3种来源于水稻、人和啤酒酵母的线粒体tRNA^Trp基因。实验表明这些线粒体tRNA^Trp的体外转录产物具有被枯草杆菌色氨酰-tRNA合成酶(TrpRS)氨酰化的能力,但是不能被鼠肝来源的氨酰tRNA合成酶粗酶所催化。动力学资源常数测定表明枯草杆菌TrpRS对线粒体tRNA^Trp的亲和力为野生型tRNA^Trp的一半,而在催化效率上,水稻和啤酒酵母线粒体tRNA^Trp的色氨酰化能力比野 相似文献
2.
用聚合酶链反应(PCR)以大肠杆菌JM83基因组DNA为模板,扩增了精氨酰-tRNA合成酶(ArgRS)基因。将该基因重组到载体pUC18上转化到大肠杆菌TG1中,得到在转化子中ArgRS的高表达。粗抽液中ArgRS的氨酰化活力,TG1和TG1转化子分别为1.65U/mg和210U/mg,后者为前者的127倍。DNA顺序测定表明,与从大肠杆菌JA200中克隆到的ArgRS基因相比913位碱基为A而不为C,这种变化使ArgRS的305位氨基酸残基由Gln变为Lys,但这种改变不影响酶的活力。 相似文献
3.
大肠杆菌精氨酰—tRNA合成酶变种ArgRS381KA的基本性质 总被引:1,自引:1,他引:0
本文研究了Ly381变为Ala的精氨酰-tRNA合成酶(ArgRS)变种ArgRS381KA的最适pH和稳态动力学性质;比较了此酶与天然酶ArgRS的荧光光谱性质和热稳定性。实验结果表明ArgRS381KA的氨酰化活力和ATP ̄PPi交换活力的最适pH分别为8.0和7.0,与天然酶相同;ArgRS381KA的氨酰化活力对精氨酸、ATP和tRNA^Arg的Km分别为12μmol/L、0.3mmol/ 相似文献
4.
大肠杆菌JM83精氨酰—tRNA合成酶基因的克隆,测序及表达 总被引:5,自引:0,他引:5
用聚合酶链反应(PCR)以大肠杆菌JM83基因组DNA为模板,扩增了精氨酰t-RNA合成酶基因,将该基因重组到载体pUC18上转化到大肠杆菌TG1中,得到在转化子中ArgRS的高表达。精抽液中ArgRS的氨酰化活力,TG1和TG1转化子分别为1.65U/mg。后者为前者的127倍,DNA顺序测定表明,与从大肠杆菌JA200中克隆到的ArgRS基因相比913位碱基为A而不为C,这种变化使ArgRS的 相似文献
5.
利用T7RNA聚合酶/启动子表达系统在大肠杆菌JM109(DE3)中表达化学合成的大鼠肝tRNA^Ile基因,经酚抽提,DEAE-52离子交换柱层极及PLC层析,分离纯化大鼠肝tRNA^Ile,变性聚丙烯酰胺凝胶电泳和Noprthern-blot鉴定表明,大鼠肝tRNA^Ile基因成功地获得表达,氨酰化活性检测表明,纯化后,每1A260(40μg)的tRNA^Ile可负载约650pmol的Ile 相似文献
6.
为研究tRNA^Trp与色氨酰-tRNA合成酶(TrpRS)的相互识别及其结构、功能关系,纯化了枯草杆菌TrpRS并用溴化氰活化的Sepharose4B将TrpRS固定化,固定化TrpRS的蛋白质回收率为为95.5%,活力回收率为31.3%。研究了固定化TrpRS的酶学性质。其热稳定性和贮存稳定性方面均比液相TrpRS有了较大的提高,最适温度、最适pH均有一定程度的增大,工作稳定性良好。以固定化T 相似文献
7.
色氨酰tRNA合成酶 (TrpRS)在蛋白质合成系统中具有非常重要的地位。通过蛋白质同源模建得到了枯草杆菌 (Bacillussubtilis)色氨酰tRNA合成酶的三维结构。模建结果对色氨酰tRNA合成酶可能与tRNATrp结合的方式给出了预测。tRNATrp是跨亚基与TrpRS相互作用的。一个tRNATrp分子的反密码环和氨基酸接受茎分别与一个TrpRS的两个亚基相互作用。图中所示 ,红色和黄色分别代表两个tRNATrp分子 ,绿色和蓝色分别代表TrpRS的两个亚基。 TheFrontCoverSh… 相似文献
8.
精胺对牛肝tRNA^lle氨基酰化的刺激作用 总被引:3,自引:0,他引:3
本实验用纯化的牛肝异亮氨酸tRNA(tRNA^Ile)和异亮氨酰tRNA合成酶,研究了精胺对Ile-tRNA复合物形成及IleRS活性的作用。结果表明:精胺能特异地促使牛肝tRNA^Ile氨基酰化反应;对IleRS活性无影响;能明显地增加形成Ile-tRNA复合物反应的Vmax和tRNA^Ile的Km值。 相似文献
9.
采用高表达大肠杆菌tRNALeu菌株提取、纯化了亮氨酸等受体转移核糖核酸tRNALeu1和tRNALeu2.利用稳态动力学手段研究了tRNALeu1及脱镁tRNALeu1在不同稀土离子作用下与纯化亮氨酰-tRNA合成酶的氨酰化作用.tRNALeu1与亮氨酰-tRNA合成酶的结合及催化效率均受参与稀土离子的影响,表观Km值有较明显的变化.结果表明,亮氨酰-tRNA合成酶催化的tRNALeu1氨酰化反应所需Mg2+能够被稀土离子取代,但亲合性能不同. 相似文献
10.
为研究tRNATrp 与色氨酰tRNA合成酶(TrpRS) 的相互识别及其结构、功能关系, 纯化了枯草杆菌TrpRS并用溴化氰活化的Sepharose 4B 将TrpRS固定化, 固定化TrpRS的蛋白质回收率为95 .5 % , 活力回收率为31.3% 。研究了固定化TrpRS的酶学性质, 其热稳定性和贮存稳定性方面均比液相TrpRS有了较大的提高, 最适温度、最适pH 均有一定程度的增大, 工作稳定性良好。以固定化TrpRS为亲和层析介质, 对含有20 个核苷酸随机序列、长度为56 个核苷酸的单链RNA 随机库进行了3 轮筛选,RNA 群体亲和固定化TrpRS的比例从4 .3 % 上升至14 .7 % 。筛选得到了与tRNATrp 氨基酸接受茎类似的RNA二级结构。实验结果表明固定化TrpRS可以作为SELEX 亲和层析介质, 进行模拟tRNATrp 分子的RNA 随机库的SELEX 筛选。 相似文献
11.
12.
13.
14.
Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis
It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis. 相似文献
15.
16.
RICHARD E. NORRIS 《Botanical journal of the Linnean Society. Linnean Society of London》1991,106(1):1-40
Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera. 相似文献
17.
JOAN VALUÈS MONTSERRAT TORRELL NÚRIA GARCIA JACAS 《Botanical journal of the Linnean Society. Linnean Society of London》2001,137(4):399-407
Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted. 相似文献
18.
肝癌中HBV和HCV基因和抗原的分布及意义 总被引:1,自引:0,他引:1
采用原位分子杂交方法检测HCV
RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV
RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV
RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV
X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV
C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细 相似文献
19.
20.
H.-R. GREGORIUS 《Biological journal of the Linnean Society. Linnean Society of London》1984,23(2-3):157-165
For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment. 相似文献
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment. 相似文献