共查询到20条相似文献，搜索用时 15 毫秒
1.
Low plasma cholesterol levels caused by a short deletion in the apolipoprotein B gene 总被引：6，自引：0，他引：6
Familial hypobetalipoproteinemia is a syndrome in which the plasma levels of apolipoprotein B (apo-B) and cholesterol are abnormally low. A truncated species of apo-B was identified in the plasma lipoproteins of members of a kindred with familial hypobetalipoproteinemia. DNA sequencing studies on genomic clones and enzymatically amplified genomic DNA samples revealed a four-base pair deletion in the apo-B gene. This short deletion, which results in a frameshift and a premature stop codon, accounts for the truncated apo-B species and explains the low apo-B and low cholesterol levels in this family. 相似文献
2.
Structure of human serum lipoproteins: nuclear magnetic resonance supports a micellar model 总被引：8，自引：0，他引：8
High-resolution proton nuclear magnetic resonance spectra of low- and high-density lipoproteins from human serum closely resemble those of dispersions of lipoprotein lipids in water. Linewidths of hydrocarbon proton absorptions are not increased in the lipoproteins. In contrast, apolar binding of lysolecithin on serum albumin causes extensive line-broadening and an upfield chemical shift of the hydrocarbon proton resonances of lysolecithin. The results are consistent with a predominantly micellar structure for the lipoproteins rather than with extensive hydrophobic association of lipid and protein. 相似文献
3.
Rudenko G Henry L Henderson K Ichtchenko K Brown MS Goldstein JL Deisenhofer J 《Science (New York, N.Y.)》2002,298(5602):2353-2358
The low-density lipoprotein receptor mediates cholesterol homeostasis through endocytosis of lipoproteins. It discharges its ligand in the endosome at pH < 6. In the crystal structure at pH = 5.3, the ligand-binding domain (modules R2 to R7) folds back as an arc over the epidermal growth factor precursor homology domain (the modules A, B, beta propeller, and C). The modules R4 and R5, which are critical for lipoprotein binding, associate with the beta propeller via their calcium-binding loop. We propose a mechanism for lipoprotein release in the endosome whereby the beta propeller functions as an alternate substrate for the ligand-binding domain, binding in a calcium-dependent way and promoting lipoprotein release. 相似文献
4.
Lipoproteins from patients receiving therapeutic doses of iodine-131 were isolated by density-gradient techniques. The binding of circulating thyroid hormones by beta lipoproteins (those of low density) was negligible. Alpha lipoproteins (those of high density) bound appreciable amounts. The bulk, however, was bound by proteins of density higher than 1.23 g/ml. 相似文献
5.
Structure, dynamics, and reactivity in hemoglobin 总被引：10，自引：0，他引：10
J M Friedman 《Science (New York, N.Y.)》1985,228(4705):1273-1280
The static structure of hemoglobin and its functional properties are very well characterized. It is still not known how energy is stored and used within the structure of the protein to promote function and functional diversity. An essential part of this question is understanding the mechanism through which the overall protein structure (quaternary structure) couples to the local environment about the oxygen binding sites. Time-resolved resonance Raman spectroscopy has been used to probe the vibrational degrees of the freedom of the binding site as a function of protein structure. Comparison of the spectra from both equilibrium and transient forms of deoxy hemoglobin from a variety of mammalian, reptilian, and fish hemoglobins reveals that for each quaternary structure there exist two tertiary states stabilized by the presence or absence of an iron-bound ligand. Pulse-probe Raman experiments show that for photodissociated, ligated hemoglobins the local tertiary structure relaxes at a solution-dependent rate extending from tens of nanoseconds to microseconds. In this local environment, the linkage between the iron and the proximal histidine proves to be the single observed structural feature that responds in a systematic and substantial manner to structural changes in the protein. The additional finding of a correlation between the frequency of the iron-proximal histidine stretching motion (nu Fe-His) and various parameters of ligand reactivity, including geminate recombination, implicates the associated localized structural element in the mechanism of protein control of ligand binding. On the basis of these and related finds, a model is presented to account for both coarse and fine control of ligand binding by the protein structure. 相似文献
6.
Garcia CK Wilund K Arca M Zuliani G Fellin R Maioli M Calandra S Bertolini S Cossu F Grishin N Barnes R Cohen JC Hobbs HH 《Science (New York, N.Y.)》2001,292(5520):1394-1398
Atherogenic low density lipoproteins are cleared from the circulation by hepatic low density lipoprotein receptors (LDLR). Two inherited forms of hypercholesterolemia result from loss of LDLR activity: autosomal dominant familial hypercholesterolemia (FH), caused by mutations in the LDLR gene, and autosomal recessive hypercholesterolemia (ARH), of unknown etiology. Here we map the ARH locus to an approximately 1-centimorgan interval on chromosome 1p35 and identify six mutations in a gene encoding a putative adaptor protein (ARH). ARH contains a phosphotyrosine binding (PTB) domain, which in other proteins binds NPXY motifs in the cytoplasmic tails of cell-surface receptors, including the LDLR. ARH appears to have a tissue-specific role in LDLR function, as it is required in liver but not in fibroblasts. 相似文献
7.
【目的】克隆内蒙古绒山羊视黄酸结合蛋白Ⅰ（cellular retinoic acid binding proteinⅠ,CRABPⅠ）基因的cDNA,进行蛋白结构的预测和表达分析,为绒山羊毛和绒形成的分子机理奠定基础。【方法】利用RT-PCR方法克隆内蒙古绒山羊CRABPⅠ基因序列,利用生物信息学方法预测其蛋白结构,采用实时荧光定量PCR探讨该基因在绒山羊4个胎儿日龄皮肤中的表达。【结果】内蒙古绒山羊CRABP I基因cDNA长679 bp（JN936490）,其开放阅读框为414 bp,氨基酸序列与其它物种相比具有较高的序列相似性。CRABP Ⅰ蛋白无明显的信号肽和跨膜区域,不存在N糖基化位点和O糖基化位点;蛋白二级结构主要由α 螺旋、β折叠和少量的转角及无规则卷曲构成。胎儿皮肤中CRABPⅠ基因在 90 d 的表达量明显高于100、120和130 d（P<0.05）。【结论】绒山羊的CRABPⅠ基因cDNA中的开放阅读框（open reading frame,ORF）在不同物种间较为保守,但种属特异性集中表现在第33和123氨基酸残基处,该基因在胎儿期的90 d表达量最大。 相似文献
8.
The elav gene product of Drosophila, required in neurons, has three RNP consensus motifs 总被引：29，自引：0，他引：29
A sequence of developmental events transforms neurons from their immature state to their mature, terminally differentiated state. The elav locus is one of the first examples of a gene that is expressed in neurons early during this developmental sequence. This gene has been shown to be required for the proper development of young neurons and for the maintenance of mature neurons. DNA sequence data presented in this report suggest that the elav gene product is an RNA binding protein, based on the presence of RNP (ribonucleoprotein) consensus sequences. This leads to the proposal that this protein is involved in the RNA metabolism of neurons. 相似文献
9.
Conserved domain such as nucleotide binding site （NBS） was found in several cloned plant disease resistance genes. Based on the NBS domain, resistance gene analogues （RGAs） have been isolated. A full-length cDNA, SPR1 was obtained by rapid amplification of cDNA ends （RACE） method. Sequence analysis indicated that the length of SPR1 was 3 066 bp, including a complete open reading frame of 2 667 bp encoding SPR1 protein of 888 amino acids. Compared with known NBS-LRR genes, it presented relatively high amino acid sequence identity. The polypeptide has a typical structure of nonT1R-NBS-LRR genes, with NB-ARC, CC, and LRR domains. The SPR1-related sequences belonged to multicopy gene family in sweetpotato genome according to the result of Southern blotting. Semi-quantitative RT-PCR analysis showed SPR1 expressed in all tested tissues. The cloning of putative resistance gene from sweetpotato provides a basis for studying the structure and function of sweetpotato disease-resistance relating genes and disease resistant genetic breeding in sweetpotato. The gene has been submitted to the GenBank database, and the accession number is EF428453. 相似文献
10.
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
11.
对葡萄血红蛋白基因的结构、进化关系、序列特征及蛋白结构进行剖析。基因结构和蛋白序列特征分析表明:尽管葡萄3个血红蛋白基因外显子个数和保守基序组织结构变异较大,但功能结构域具有高度保守性。结构模拟显示,葡萄VvHb1以单体形式存在,而VvHb2和VvHb3则以二聚体形式存在,尽管它们三维构象以螺旋结构为主,但结合血红素分子活性不同。进化分析揭示,植物血红蛋白具有4个类群,其中葡萄的血红蛋白落入主要类群外,并且单独形成了一个进化分支,说明葡萄血红蛋白基因在物种形成后发生了快速进化和基因扩增现象。 相似文献
12.
[目的]克隆构建黄曲霉毒素B1(AFB1)单链抗体(scFv)基因,并对其编码蛋白序列和结构进行分析预测,为scFv分子修饰改造及在免疫学检测中的应用提供参考依据.[方法]以抗AFB1单克隆抗体杂交瘤细胞株为原料,通过PCR扩增重链可变区(VH)和轻链可变区(VL),以(Gly4Ser)3为柔性接头(Linker)拼接构建抗AFB1 scFv基因,并采用在线生物信息学分析软件对其氨基酸序列、理化性质及蛋白结构进行分析预测.[结果]抗AFB1 scFv基因全长744 bp,编码248个氨基酸,分子量为26312.05 Da,理论等电点(pI)5.70,其二级结构中含有35个α-螺旋(占14.11%)、28个β-折叠(占11.29%)、85个延伸链(占34.28%)和100个随机卷曲(占40.32%),在三级结构中连接肽卷曲将VH和VL区域牵拉而相互靠近,形成典型的抗体结构——沟槽结构,是scFv的抗原结合区域.[结论]构建的抗AFB1 scFv其VH含有117个氨基酸、VL含有116个氨基酸,具备典型抗体结构——沟槽结构,能与抗原特异性结合. 相似文献
13.
[目的]克隆甘蔗ATP结合蛋白基因,分析其基本生物学信息及在干旱胁迫下的表达特性,为ATP结合蛋白的功能研究提供理论依据.[方法]从乙烯诱导甘蔗差异表达转录组和水分胁迫下甘蔗cDNA文库中获取ATP结合蛋白基因序列,设计其引物进行RT-PCR扩增,利用生物信息学软件进行序列分析及其蛋白结构和功能预测,并采用实时荧光定量PCR(qPCR)检测干旱胁迫处理下的甘蔗ATP结合蛋白基因的表达情况.[结果]克隆获得的甘蔗ATP结合蛋白基因全长2145bp,编码714个氨基酸,其蛋白分子质量为79.430kD,理论等电点(pI)为9.33,不稳定系数为44.38;甘蔗ATP结合蛋白与玉米ATP结合蛋白的核苷酸序列及其推导氨基酸系列同源性最高,均达93%.甘蔗ATP结合蛋白主要由无规则卷曲(42.02%)、α螺旋(25.63%)和延伸链(22.27%)结构组成,具有蛋白激酶催化结构域、ATP结合位点、核苷酸结合位点(NBS)、糖基化位点、激酶磷酸化结合位点及核定位信号等;甘蔗ATP结合蛋白可能主要定位在细胞核、叶绿体、线粒体和过氧化物酶体中,起中间代谢调控作用,或参与转录调控、免疫应答、胁迫应答及信号转导等生物反应.qPCR检测结果显示,在干旱胁迫7d后,甘蔗ATP结合蛋白基因的表达量明显下调,约为对照的30%,恢复正常供水(复水)后,表达量回升.[结论]甘蔗ATP结合蛋白基因表达受干旱胁迫诱导,可能参与甘蔗对干旱逆境胁迫响应的代谢调控. 相似文献
14.
Expression of the familial hypercholesterolemia gene in heterozygotes: mechanism for a dominant disorder in man 总被引：16，自引：0，他引：16
Studies in ctltured fibroblasts indicate that the primary genetic abnormality in familial hypercholesterolemia involves a deficiency in a cell surface receptor for low density lipoproteins (LDL). In normal cells, binding of LDL to this receptor regulates cholesterol metabolism by suppressing cholesterol synthesis and increasing LDL degradation. In cells from heterozygotes, a 60 percent reduction in LDL receptors leads to a concentration-dependent defect in regulation, so that attainment of equal rates of cholesterol synthesis and LDL degradation in normal and heterozygous cells requires a two- to threefold higher concentration of LDL in the heterozygote. The identification of this genetic regulatory defect in fibroblasts of heterozygotes makes available an in vitro system for studying the effects of a dominant mutation on gene expression in mammalian cells. 相似文献
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植物抗病基因类似序列的研究进展及应用策略 总被引：5，自引：0，他引：5
植物抗病基因克隆对抗病育种和抗病机制的研究具有重要意义。对已克隆出的基因研究表明,大多数的抗病基因都具有高度保守的结构域(如NBS,LRR,LZ,STK和TIR等)。根据这些保守区域设计核苷酸引物,通过PCR技术已经获得很多的RGA,然后以此为探针筛选DNA或cDNA文库,最终可获得抗病基因的候选克隆,这就是新近发展起来的同源序列克隆技术。文章简述了对抗病基因的结构特征,同源序列克隆技术及其应用策略。 相似文献
18.
A protein that binds to a cis-acting element of wheat histone genes has a leucine zipper motif 总被引：34，自引：0，他引：34
T Tabata H Takase S Takayama K Mikami A Nakatsuka T Kawata T Nakayama M Iwabuchi 《Science (New York, N.Y.)》1989,245(4921):965-967
19.
为研究人、猪、大鼠、小鼠中klf家族的进化特征,笔者用Clustal X 和MEGA ,在线软件GSGD,K estimator和PAML,在线软件MEME\\MAST和InterProScan,PSORT II分别构建进化亲缘关系树、分析基因结构、鉴定选择压力、注释蛋白质模体和确定核定位信号。结果显示：进化亲缘树及基因结构分析都将KLF家族分为α,β,γ,δ和ε 5个亚类,亚类内各基因结构相似,家族各成员基因随机分布于不同染色体,klf1 和 klf2紧密簇集,猪 klf17 定位于6号染色体而非15号染色体,猪的两对旁系同源基因：klf9和klf9a,klf10和klf10a,及相似家族成员klf1和klf2,分别起源于近期和远期的基因串联复制事件;适应性进化选择压力分析表明,klf13和klf17经历了正选择,其他基因都受到严格的负选择作用;KLF蛋白羧基端都有3个高度保守的串联锌指结构,核定位信号（NLS）位于3串联锌指内或其紧邻上游,氨基端模体则相对多样化,KLF3,KLF4,KLF8和KLF12以其共有的PVDLS/T模体（单字母氨基酸缩写）结合转录辅因子CtBP (C terminus binding protein)进而调控靶基因转录,KLF9,KLF10,KLF11,KLF13,KLF14和KLF16共享转录辅因子Sin3结合结构域SID（Sin3 interacting domain）,KLF7中发现的亮氨酸拉链模体表明其以二聚体的形式参与转录调控。klf家族基因结构和氨基端模体的多样化、羧基端保守锌指结构及进化中经历的负选择压力表明家族进化中经历了转录调控方式和调控功能的多样化,同时保留了结合富含GC启动子的基本模式。 相似文献
20.
T M Williams D Moolten J Burlein J Romano R Bhaerman A Godillot M Mellon F J Rauscher J A Kant 《Science (New York, N.Y.)》1991,254(5039):1791-1794