共查询到20条相似文献，搜索用时 15 毫秒
1.
《Science (New York, N.Y.)》1994,264(5163):1240
The enzyme shown in the photo on page 1363 accompanying the 11 March ScienceScope item "Lobbying backfires on LBL, Berkeley" was not a "designed enzyme" or an engineered protein, nor was it human glutathione S-transferase. It is a representation of the mu 3-3 isozyme of rat liver glutathione S-transferase with an inhibitor, 9-(S-glutathionyl)-10-hydroxy-9, 10-dihydrophenanthrene. The structure was determined at the Center for Advanced Research in Biotechnology as a result of collaborative work between the laboratory of Gary L. Gilliland and that of Richard Armstrong in the Department of Chemistry and Biochemistry at the University of Maryland, College Park [X. Ji et al., Biochemistry 33, 1043 (1994)]. 相似文献
2.
以芸薹种(Brassica campestrisL.,syn.B.rapaL.)的3个亚种,即白菜(B.campestrisL.ssp.chinensisM ak ino)、大白菜(B.campestrisssp.pekinensisO lsson)和芜菁(B.campestrisssp.rapifera(Matzg.)S insk)等芸薹作物为研究材料,对其杂种优势形成进行同工酶和蛋白质分析,结果表明:不同品种在同一生育期或同一品种在不同生育期酶谱和蛋白质表型有差异,但把各品种不同生育期的谱带叠加,所得到的总谱带是相同的;品种间杂交其F1的同工酶和蛋白质谱带不存在“杂种带”或“互补带”;酶谱和蛋白质表型上的差异,可能是芸薹属作物杂种优势产生的生理基础之一。 相似文献
3.
Tyrosinase inhibition: its role in suntanning and in albinism 总被引：5，自引：0，他引：5
Tyrosinase inhibitor (molecular weight less than 5000; extracted from various melanomas) fully inhibits soluble tyrosinase but only partially inhibits tyrosinase "aggregated" into melanosomes; the inhibitor can be inactivated by ultraviolet light. S91 Albinotyrosinase Type B apparently cannot "aggregate" into melanosomes because its protein carrier is genetically altered. Therefore, albinotyrosinase remains vulnerable to its inhibitor and cannot produce melanin, even though the enzyme has a functioning active center. 相似文献
4.
[目的]研究"琉球红"对低温的耐受能力。[方法]试验采用盆栽方法,以"琉球红"杜鹃为试验材料,研究了"琉球红"杜鹃叶片中3种保护酶活性[过氧化氢酶(CAT)、过氧化物酶(POD)和超氧化物歧化酶(SOD)]、相对电导率、丙二醛(MDA)含量、可溶性蛋白含量等理化指标,在0、-3和-6℃(T_1、T_2和T_3)低温条件下,处理1、2、3、4、5、6 d时的变化情况。[结果]在低温胁迫下"琉球红"杜鹃叶片中MDA含量,可溶性蛋白含量,及"琉球红"杜鹃叶片保护酶CAT、POD和SOD活性先升高,且在低温胁迫4 d时,MDA含量、可溶性蛋白含量和酶活性达到最高,随着低温胁迫时间的增加,MDA含量、可溶性蛋白含量和保护酶活性开始下降,在低温胁迫6 d时达到最低,且杜鹃叶片出现轻微萎蔫情况与对照变化较为明显。试验证明"琉球红"杜鹃在-6℃低温胁迫3 d内保持着正常的生理指标,在低温胁迫3 d后,包括外部形态特征、保护酶活性均发生较明显变化。在低温胁迫下"琉球红"杜鹃通过提高保护酶活性及可溶性蛋白含量等,减少了活性氧(ROS)的积累和膜脂过氧化产物的产生,增强了"琉球红"杜鹃耐低温胁迫的能力,但是随着低温胁迫时间的增加,植物细胞受到不可逆的破坏,导致抗氧化酶活性下降,试验表明,"琉球红"杜鹃能耐受的较低温度为-3℃。[结论]该研究可为宁波及周边城市将"琉球红"作为绿化植物提供参考。 相似文献
5.
Design, activity, and 2.8 A crystal structure of a C2 symmetric inhibitor complexed to HIV-1 protease 总被引：22，自引：0，他引：22
J Erickson D J Neidhart J VanDrie D J Kempf X C Wang D W Norbeck J J Plattner J W Rittenhouse M Turon N Wideburg 《Science (New York, N.Y.)》1990,249(4968):527-533
A two-fold (C2) symmetric inhibitor of the protease of human immunodeficiency virus type-1 (HIV-1) has been designed on the basis of the three-dimensional symmetry of the enzyme active site. The symmetric molecule inhibited both protease activity and acute HIV-1 infection in vitro, was at least 10,000-fold more potent against HIV-1 protease than against related enzymes, and appeared to be stable to degradative enzymes. The 2.8 angstrom crystal structure of the inhibitor-enzyme complex demonstrated that the inhibitor binds to the enzyme in a highly symmetric fashion. 相似文献
6.
Crystal structure of the catalytic subunit of cyclic adenosine monophosphate-dependent protein kinase 总被引：117，自引：0，他引：117
D R Knighton J H Zheng L F Ten Eyck V A Ashford N H Xuong S S Taylor J M Sowadski 《Science (New York, N.Y.)》1991,253(5018):407-414
The crystal structure of the catalytic subunit of cyclic adenosine monophosphate-dependent protein kinase complexed with a 20-amino acid substrate analog inhibitor has been solved and partially refined at 2.7 A resolution to an R factor of 0.212. The magnesium adenosine triphosphate (MgATP) binding site was located by difference Fourier synthesis. The enzyme structure is bilobal with a deep cleft between the lobes. The cleft is filled by MgATP and a portion of the inhibitor peptide. The smaller lobe, consisting mostly of amino-terminal sequence, is associated with nucleotide binding, and its largely antiparallel beta sheet architecture constitutes an unusual nucleotide binding motif. The larger lobe is dominated by helical structure with a single beta sheet at the domain interface. This lobe is primarily involved in peptide binding and catalysis. Residues 40 through 280 constitute a conserved catalytic core that is shared by more than 100 protein kinases. Most of the invariant amino acids in this conserved catalytic core are clustered at the sites of nucleotide binding and catalysis. 相似文献
7.
Structure of a peptide inhibitor bound to the catalytic subunit of cyclic adenosine monophosphate-dependent protein kinase 总被引：69，自引：0，他引：69
D R Knighton J H Zheng L F Ten Eyck N H Xuong S S Taylor J M Sowadski 《Science (New York, N.Y.)》1991,253(5018):414-420
The structure of a 20-amino acid peptide inhibitor bound to the catalytic subunit of cyclic AMP-dependent protein kinase, and its interactions with the enzyme, are described. The x-ray crystal structure of the complex is the basis of the analysis. The peptide inhibitor, derived from a naturally occurring heat-stable protein kinase inhibitor, contains an amphipathic helix that is followed by a turn and an extended conformation. The extended region occupies the cleft between the two lobes of the enzyme and contains a five-residue consensus recognition sequence common to all substrates and peptide inhibitors of the catalytic subunit. The helical portion of the peptide binds to a hydrophobic groove and conveys high affinity binding. Loops from both domains converge at the active site and contribute to a network of conserved residues at the sites of magnesium adenosine triphosphate binding and catalysis. Amino acids associated with peptide recognition, nonconserved, extend over a large surface area. 相似文献
8.
Three pairs of near-isogenic lines with different genetic backgrounds of yellow-seeded and black-seeded rape (Brassica napus L.) were used as experiment materials to study the relationship of color formation in the seedcoat with enzyme activity and protein content in it. The results showed that with similar genetic backgrounds, phenylalanine ammonia-lyase (PAL) and polyphenol oxidase(PPO) activities in the black-seeded lines were much higher than in their yellow-seeded counterparts and maximum PAL activity in the seedcoat occurred comparatively late while no significant difference was present in glutamine synthetase (GS) between the two types of rape. The plants were treated with red light,blue light, p-hydroxybenzoic acid (a PAL inhibitor), polyvinylpyridoxal (a PPO inhibitor),urea (a protein synthesis promoter) or chloramphenicol (CM, a plastid protein synthesis inhibitor) during seed development. It is speculated that PAL may be primarily responsible for coloration in the yellow seed; PPO may be the main factor contributing to the darkness of the testa of the black genotypes; and nitrogen assimilation is, probably, not directly related to the difference in protein content observed between yellow- and black-seeded genotypes, which may be induced mainly by PAL. 相似文献
9.
大豆质核互作雄性不育系NJCMS1A及其保持系的花药差异蛋白质组学研究 总被引：8，自引：2，他引：8
【目的】对大豆质核互作雄性不育系NJCMS1A及其同型保持系NJCMS1B的二胞花粉期花药进行差异蛋白质组学研究，探讨大豆质核互作雄性不育的分子机制。【方法】采用双向凝胶电泳技术对其蛋白质进行分离，凝胶用考马斯亮蓝染色，使用PDQuest软件分析蛋白质图谱，利用基质辅助激光解吸飞行时间质谱（MALDI-TOF-MS）技术对差异表达蛋白进行质谱分析，获得肽质量指纹图谱，用Profound和Mascot软件搜索NCBInr数据库，初步鉴定差异表达蛋白并分析其功能。【结果】 在分子量18.4～116.0 kD、等电点4～7线性范围内，检测到约212个蛋白点，差异表达蛋白点24个。其中10个在NJCMS1A 中出现而在NJCMS1B中缺失，12个在NJCMS1A中缺失而在NJCMS1B中出现，2个表达量在NJCMS1B中比在NJCMS1A中明显增强。鉴定出11个差异表达蛋白，其中7个在NJCMS1A中出现而在NJCMS1B中缺失，4个在NJCMS1A中缺失而在NJCMS1B中出现。【结论】对主要差异表达蛋白如ACC氧化酶、半胱氨酸蛋白酶、V型H+-ATP酶A亚基、MADS盒蛋白、淀粉分枝酶和UDP-葡萄糖焦磷酸化酶等进行功能分析，推测不育系NJCMS1A雄性不育性可能与能量代谢紊乱、细胞程序化死亡（PCD）、乙烯过度合成、淀粉合成受抑制和花器官发育调节基因作用失控等有关。 相似文献
10.
2-Mercaptobenzothiazole is an exceptionally potent inhibitor of banana polyphenoloxidase; it significantly delays the onset of substrate oxidation at concentrations as low as 10(-7)M and causes prolonged inhibition at 2 x 10(-5)M or higher. Inhibition results from formation of a dissociable, mixed complex between the enzyme and the inhibitor. 相似文献
11.
B A Jameson P E Rao L I Kong B H Hahn G M Shaw L E Hood S B Kent 《Science (New York, N.Y.)》1988,240(4857):1335-1339
The human immunodeficiency virus type 1 (HIV-1) uses the CD4 protein as a receptor for infection of susceptible cells. A candidate structure for the HIV-1 binding site on the CD4 protein was identified by epitope mapping with a family of eight functionally distinct CD4-specific monoclonal antibodies in conjunction with a panel of large CD4-derived synthetic peptides. All of the seven epitopes that were located reside within two immunoglobulin-like disulfide loops situated between residues 1 and 168 of the CD4 protein. The CD4-specific monoclonal antibody OKT4A, a potent inhibitor of HIV-1 binding, recognized a site between residues 32 and 47 on the CD4 protein. By analogy to other members of the immunoglobulin superfamily of proteins, this particular region has been predicted to exist as a protruding loop. A synthetic analog of this loop (residues 25 to 58) showed a concentration-dependent inhibition of HIV-1-induced cell fusion. It is proposed that a loop extending from residues 37 to 53 of the CD4 protein is a binding site for the AIDS virus. 相似文献
12.
Platelet coagulation factor XIa-inhibitor, a form of Alzheimer amyloid precursor protein 总被引：11，自引：0，他引：11
An inhibitor of coagulation factor XIa was purified from serum-free conditioned medium of HepG2 liver cells. Platelets stimulated with thrombin or calcium ionophore (A23187) secrete a protein functionally and immunologically identical to the inhibitor, implying a role for this inhibitor in hemostasis. Analysis of the amino-terminal amino acid sequence and immunologic reactivity showed the inhibitor to be a truncated form of the Alzheimer's amyloid precursor protein that contains a Kunitz-type serine protease inhibitor domain and at least a portion of the amyloid beta protein. It inhibits factor XIa and trypsin with a Ki of 450 +/- 50 pM and 20 +/- 10 pM, respectively. Heparin (1 unit/ml) did not significantly effect inhibition of trypsin, but inhibition of XIa was 15 times greater (Ki = 25 +/- 15 pM) in the presence of heparin. 相似文献
13.
柿子单宁对几种蛇毒中主要酶的抑制作用及其机理初探 总被引：2，自引：0，他引：2
【目的】分析柿子单宁（persimmon tannin,PT）对江浙蝮蛇、尖吻蝮蛇、眼镜蛇毒中主要酶活力的抑制作用,初步研究两者相互作用的机理。【方法】将蛇毒与PT以不同比例混合后在37℃下温育1 h,离心分离,测定上清液中主要酶活力变化,并采用SDS-聚丙烯酰胺凝胶电泳对粗毒和作用后所得沉淀及上清液进行分析。【结果】当蛇毒与PT质量比达到1﹕1时,粗毒中蛋白质水解酶、磷脂酶A2、L-氨基酸氧化酶、精氨酸酯酶、乙酰胆碱酯酶、类凝血酶活力被完全抑制,且酶活力的下降与PT含量呈剂量增加效应;SDS-聚丙烯酰胺电泳表明,PT与蛇毒蛋白具有很强的非特异性结合能力。但对不同结构蛋白质结合能力和选择性也明显不同。【结论】柿子单宁在体外条件下对蛇毒中几种酶的活力具有明显的抑制作用,PT与蛋白结合是导致酶失活的重要原因。 相似文献
14.
外源添加抑制剂对芦蒿吸收Cd和Pb的影响 总被引：5，自引：4，他引：1
以水生植物芦蒿为试验材料,通过人工培养液温室培养方法,研究了代谢抑制剂、P-型ATP酶抑制剂、蛋白合成抑制剂、离子通道抑制剂对芦蒿吸收Cd和Pb的影响.结果表明,代谢抑制剂(Na_3N)和P-型ATP酶抑制剂(Na_3VO_4)对芦蒿Cd和Pb的吸收均有一定的抑制作用,说明芦蒿对Cd和Pb存在主动吸收.钙离子通道抑制剂LaCl_3显著抑制芦蒿根部对Cd的吸收,而对Pb的吸收没有明显的抑制作用,说明芦蒿对Cd的吸收与钙离子通道有关;蛋白质合成抑制剂放线菌酮(CHD)对芦蒿Cd和Pb的吸收有显著的抑制作用,说明芦蒿对Cd和Pb的吸收与一些蛋白质或酶的诱导合成及其活性密切相关. 相似文献
15.
The regulatory domain of protein kinase C contains an amino acid sequence between residues 19 and 36 that resembles a substrate phosphorylation site in its distribution of basic residue recognition determinants. The corresponding synthetic peptide (Arg19-Phe-Ala-Arg-Lys-Gly-Ala25-Leu-Arg-Gln-Lys-Asn-Val-His -Glu-Val-Lys-Asn36) acts as a potent substrate antagonist with an inhibitory constant of 147 +/- 9 nM. It is a specific inhibitor of protein kinase C and inhibits both autophosphorylation and protein substrate phosphorylation. Substitution of Ala25 with serine transforms the pseudosubstrate into a potent substrate. These results demonstrate that the conserved region of the regulatory domain (residues 19 to 36) of protein kinase C has the secondary structural features of a pseudosubstrate and may be responsible for maintaining the enzyme in the inactive form in the absence of allosteric activators such as phospholipids. 相似文献
16.
Structure of E. coli glutaminyl-tRNA synthetase complexed with tRNA(Gln) and ATP at 2.8 A resolution 总被引：96，自引：0，他引：96
The crystal structure of Escherichia coli glutaminyl-tRNA synthetase (GlnRS) complexed with its cognate glutaminyl transfer RNA (tRNA(Gln] and adenosine triphosphate (ATP) has been derived from a 2.8 angstrom resolution electron density map and the known protein and tRNA sequences. The 63.4-kilodalton monomeric enzyme consists of four domains arranged to give an elongated molecule with an axial ratio greater than 3 to 1. Its interactions with the tRNA extend from the anticodon to the acceptor stem along the entire inside of the L of the tRNA. The complexed tRNA retains the overall conformation of the yeast phenylalanine tRNA (tRNA(Phe] with two major differences: the 3' acceptor strand of tRNA(Gln) makes a hairpin turn toward the inside of the L, with the disruption of the final base pair of the acceptor stem, and the anticodon loop adopts a conformation not seen in any of the previously determined tRNA structures. Specific recognition elements identified so far include (i) enzyme contacts with the 2-amino groups of guanine via the tRNA minor groove in the acceptor stem at G2 and G3; (ii) interactions between the enzyme and the anticodon nucleotides; and (iii) the ability of the nucleotides G73 and U1.A72 of the cognate tRNA to assume a conformation stabilized by the protein at a lower free energy cost than noncognate sequences. The central domain of this synthetase binds ATP, glutamine, and the acceptor end of the tRNA as well as making specific interactions with the acceptor stem.2+t is 相似文献
17.
18.
Walden WE Selezneva AI Dupuy J Volbeda A Fontecilla-Camps JC Theil EC Volz K 《Science (New York, N.Y.)》2006,314(5807):1903-1908
Iron regulatory protein 1 (IRP1) binds iron-responsive elements (IREs) in messenger RNAs (mRNAs), to repress translation or degradation, or binds an iron-sulfur cluster, to become a cytosolic aconitase enzyme. The 2.8 angstrom resolution crystal structure of the IRP1:ferritin H IRE complex shows an open protein conformation compared with that of cytosolic aconitase. The extended, L-shaped IRP1 molecule embraces the IRE stem-loop through interactions at two sites separated by approximately 30 angstroms, each involving about a dozen protein:RNA bonds. Extensive conformational changes related to binding the IRE or an iron-sulfur cluster explain the alternate functions of IRP1 as an mRNA regulator or enzyme. 相似文献
19.
【目的】在前期克隆了绿盲蝽水溶性海藻糖酶（ALTre-1）基因的基础上,以获得具有酶活性的重组蛋白,明确酶促反应的最佳pH值及最适温度,为绿盲蝽海藻糖酶分子调控机制及其抑制剂的应用研究奠定基础。【方法】将含有绿盲蝽ALTre-1基因的T载体经Nde I和Not I双酶切,构建ALTre-1基因原核表达载体（pET28a-ALTre-1）,表达载体经诱导表达和蛋白纯化,获得ALTre-1功能区纯化蛋白。在蛋白浓度为0.3 mg•mL-1的条件下,以海藻糖为底物,对纯化得到的重组Tre-1蛋白进行活性检测,确定其酶促反应的最佳pH值和最佳温度。【结果】ALTre-1基因在大肠杆菌中BL21中能够高效表达,纯化获得的重组蛋白在试验条件下有较高的海藻糖酶水解活性（（184.83±13.39）nmol•μg-1•min-1）。重组ALTre-1蛋白活性最适pH值为7.0（酶活性为（202.04±13.76）nmol•μg-1•min-1）,表明重组ALTre-1蛋白是1个在中性环境中具有最佳活性的海藻糖酶,同时重组ALTre-1蛋白酶活性最适温度为55℃（酶活性为（228.59±4.62）nmol•μg-1•min-1）。【结论】本研究克隆得到了ALTre-1全长基因,获得了具有海藻糖酶活的重组蛋白,该重组蛋白在pH 7.0、温度55℃条件下酶活性最高。 相似文献
20.
【目的】鉴定大豆抗逆相关转录因子GmDREB5的互作蛋白,分析其互作蛋白GmUBC13的特性及其生物学功能,解析GmDREB5提高植物抗逆性的分子机制。【方法】通过酵母双杂交系统,以大豆GmDREB5的AP2功能域为诱饵对干旱处理的大豆cDNA文库进行筛选,获得GmDREB5候选互作蛋白后通过酵母互作及体外Pull-down试验确定GmDREB5与候选蛋白之间的互作关系;同时,分析互作蛋白GmUBC13的进化关系、蛋白结构及亚细胞定位等特性;通过半定量RT-PCR分析其互作蛋白GmUBC13在干旱、高盐、低温等非生物胁迫和激素ABA处理下的表达谱;通过转化烟草鉴定GmUBC13的生物学功能。【结果】通过筛选大豆干旱处理的cDNA文库获得一个GmDREB5互作蛋白GmUBC13（ubiquitin conjugating enzyme 13）,GmUBC13属于泛素结合酶蛋白家族,GmUBC13含有UBCc保守域（ubiquitin-conjugating enzyme catalytic domain）、与泛素连接酶E3互作的氨基酸残基以及高度保守的半胱氨酸催化位点。进化树分析表明,GmUBC13的氨基酸序列与拟南芥（Arabidopsis thaliana）含有16个成员的E2家族的第XV亚组的AtUBC13A、AtUBC13B以及水稻（Oryza sativa）的泛素结合酶蛋白Os01g0673600分别具有99%、97%和97%的同源性。酵母互作试验及体外Pull-down分析证明GmUBC13与GmDREB5蛋白之间存在相互作用。表达特性分析表明,GmUBC13受干旱、高盐、低温等非生物胁迫和激素ABA处理的诱导表达。GmUBC13在ABA的胁迫条件下,1 h开始有表达,10 h时表达量上升到最大,24 h稍微降低;在干旱和盐胁迫条件下,1 h开始表达,并随着胁迫时间的增长,表达量逐渐上升,24 h表达量达到最大;在低温胁迫条件下,GmUBC13受诱导较快,5 h表达达到最大,在10 h和24 h时未表达。蛋白亚细胞定位结果显示,GmDREB5蛋白定位在细胞核和细胞膜上,GmUBC13定位在细胞核中。基因功能鉴定结果证明,过表达GmUBC13的转基因株系GmUBC13-1、GmUBC13-2和受体对照W38的幼苗在正常MS培养基上的生长状态基本相似,在不同浓度PEG胁迫条件下,转基因株系GmUBC13-1、GmUBC13-2和W38烟草叶片叶绿素含量都降低,根长和地上部生长都受到抑制,而转GmUBC13烟草的叶片叶绿素含量降低缓慢,转基因烟草各株系的根长、地面长度均高于对照W38,且在8% PEG处理条件下,转基因株系GmUBC13-2的叶绿素含量、根长及地面长度与W38的差异达极显著。将生长2周的转基因烟草株系GmUBC13-1、GmUBC13-2与W38移至营养土中控水处理21 d,复水处理6 d后显示,转基因烟草株系生长情况明显优于非转基因对照W38,且转基因株系的存活率显著高于对照W38,表明在烟草中过表达大豆GmUBC13可以显著提高转基因烟草的抗旱性。【结论】大豆泛素连接酶GmUBC13与抗逆相关转录因子GmDREB5互作,GmUBC13受各种非生物胁迫处理诱导表达,在烟草中过表达可以显著提高植物的抗旱性。 相似文献