转铁蛋白的研究与发展

转铁蛋白（Transferrin,Tf,又称为铁传递蛋白、运铁蛋白）是一种重要的β－球蛋白,是脊椎动物体内铁的运输者。自1945年Holmberg和Laurell首次在人血清中发现这种非血红素结合铁的转铁蛋白以来^[1],人们又在猪等其它哺乳动物以及鱼类、两栖类及爬行类的血清中发现Tf的存在^[2],随后又相继发现了乳Tf和卵Tf以及Tf的蛋白类似物。由于Tf具有特殊的生理功能,Tf的研究一直受到国际上生命科学工作者的关注,人们已对许多属Tf的结构与功能做了大量研究。     

转铁蛋白糖链结构对其受体亲和性的影响

用伴刀豆凝集素,小扁豆凝集素和欧曼陀罗凝集素亲和层析法,分别从正常人血清转铁蛋白和孕妇血清Ｔｆ中获得二天线糖链Ｔｆ和多天线糖链的Ｔｆ,用于研究其对胎盘中纯化得到的转铁蛋白受体和亲和性。经Ｓｃａｔｃｈａｒｄ作图结果发现,表明含多天线糖链的Ｔｆ对受体的亲和性比二天线糖链的Ｔｆ降低１倍,而ＴｆＲ的结合位点数不变。     

转铁蛋白糖链结构对受体亲和性的影响

用伴刀豆凝集素（ＣｏｎＡ）,小扁豆凝集素（ＬＣＡ）,和欧曼陀罗凝集素（ＤＳＡ）亲和层析法,分别从正常人血清转铁蛋白（Ｔｆ）和孕妇血清Ｔｆ中获得二天线糖链的Ｔｆ和多天线糖链的Ｔｆ．用于研究其对从胎盘中纯化得到的转铁蛋白受体（ＴｆＲ）的亲和性。经Ｓｃａｔｃｈａｒｄ作图结果发现,解离常数分别为：４．９７×１０－８ｍｏｌ／Ｌ和９．８０×１０－８ｍｏｌ／Ｌ．最大结合分别是１８０ｆｍｏｌ／Ｌ和１８２ｆｍｏｌ／Ｌ,表明含多天线糖链的Ｔｆ对受体的亲和性比二天线糖链的Ｔｆ降低１倍,而ＴｆＲ的结合位点数不变。     

转铁蛋白/转铁蛋白受体介导的药物运输

转铁蛋白 转铁蛋白受体介导的铁吸收过程是哺乳动物吸收铁的主要途径。近几十年的研究 ,对此过程有了充分了解。作为靶向配体 ,转铁蛋白可以介导多种金属的运输。最新研究表明转铁蛋白可以与抗癌药物、蛋白质、基因等形成复合物 ,靶向肿瘤、血脑屏障、快速分裂等大量表达转铁蛋白受体的组织。转铁蛋白偶联的药物具有靶向性强、毒副小的优点。综述了转铁蛋白 转铁蛋白受体介导的药物运输的最新研究进展。     

绒山羊转铁蛋白多态性的研究

绒山羊转铁蛋白多态性的研究ＴＲＡＮＳＦＥＲＲＩＮＰＯＬＹＭＯＲＰＨＩＳＭＩＮＣＡＳＨＭＥＲＥＧＯＡＴ关键词绒山羊，转铁蛋白，多态性ＫｅｙｗｏｒｄｓＣａｓｈｍｅｒｅｇｏａｔ，Ｔｒａｎｓｆｅｒｉｎ，Ｐｏｌｙｍｏｒｐｈｉｓｍ转铁蛋白（ｔｒａｎｓｆｅｒｉｎ，...     

文昌鱼转铁蛋白及转铁蛋白的分子进化

从厦门文昌鱼分离纯化了文昌鱼转铁蛋白,物化性质与青岛文昌鱼转铁蛋白相同,其单体和二聚体的分子量分别为２６ｋＤ和５２ｋＤ,是一分子量约为脊椎动物转铁蛋白１／４的糖蛋白,测定了文昌鱼转铁蛋白完整分子和其Ｃ端分子片段的部分氨基酸序列并分析 一人务清失蛋白氨基酸序列的同源性。发现用文昌鱼转铁蛋白序列可将人血清转铁蛋白序列划分成粗略相等的４个片段,文是鱼转铁蛋白与每一片段及人血清转铁蛋白的４个片段之间存在明     

人血清转铁蛋白遗传多态性与疾病相关的研究

本文应用等电聚焦电泳技术,调查了广州地区128例白血病、80例原发性肝癌、52例系统性红斑狼疮和1456例正常人的Tf遗传多态性分布。与正常人组相比,急性粒细胞白血病组的Tf~(C_1)基因频率显著增高(P<0.05);TfC_1C_1表型频率也显著高于正常人组(P<0.05),TfC_1C_1人群的患病相对危险率为1.9。未发现急性淋巴细胞白血病、慢性粒细胞白血病、原发性肝癌疾病组的Tf表型和基因频率与正常人组有显著性统计学差异。此外,还发现系统性红斑狼疮组的Tf~(C_2)基因频率显著高于正常人(P<0.025),Tf~(C_1)频率则相应下降(P<0.05);表型频率TfC_1C_2显著增高(P<0.005),相对危险率为2.3,TfC_1C_2相应下降(P<0.01)。     

鲤转铁蛋白和血清酯酶多态性研究

鱼类血清蛋白多态性研究,在国内外已有不少报道。其中研究最为广泛的是转铁蛋白(Transferrn;Tf)该蛋白质不同等位基因的差异表达。可以作为品系鉴定和遗传育种的可靠的生化遗传指标。有关鲤的血清蛋白多态性研究,国内尚未见     

Protocol to determine accurate absorption coefficients for iron-containing transferrins

An accurate protein concentration is an essential component of most biochemical experiments. The simplest method to determine a protein concentration is by measuring the A₂₈₀ using an absorption coefficient (ε) and applying the Beer-Lambert law. For some metalloproteins (including all transferrin family members), difficulties arise because metal binding contributes to the A₂₈₀ in a nonlinear manner. The Edelhoch method is based on the assumption that the ε of a denatured protein in 6 M guanidine-HCl can be calculated from the number of the tryptophan, tyrosine, and cystine residues. We extend this method to derive ε values for both apo- and iron-bound transferrins. The absorbance of an identical amount of iron-containing protein is measured in (i) 6 M guanidine-HCl (denatured, no iron), (ii) pH 7.4 buffer (nondenatured with iron), and (iii) pH 5.6 (or lower) buffer with a chelator (nondenatured without iron). Because the iron-free apoprotein has an identical A₂₈₀ under nondenaturing conditions, the difference between the reading at pH 7.4 and the lower pH directly reports the contribution of the iron. The method is fast and consumes approximately 1 mg of sample. The ability to determine accurate ε values for transferrin mutants that bind iron with a wide range of affinities has proven to be very useful; furthermore, a similar approach could easily be followed to determine ε values for other metalloproteins in which metal binding contributes to the A₂₈₀.     

The competition between transferrins labeled with59Fe,65Zn, and54Mn for the binding sites on lactating mouse mammary gland cells

Using a homologous competition of⁵⁴Mn-transferrin with Mntransferrin and⁶⁵Zn-transferrin with Zn-transferrin, it was found that on the plasma membrane of lactating mouse mammary gland cells there are receptor binding Mn-transferrin and Zn-transferrin. The heterologous competition between labeled and nonlabeled Fe-transferrin, Mn-transferrin and Zn-transferrin, as well as almost equal affinity constants of cellular receptors toward the three metals by competition of Fe-transferrin suggests that one and the same receptor accepts all three metals from the transferrin molecule. The cell receptors therefore possess a polymetal binding function. A model and a mechanism for regulation of the transport metal flow toward the mammary gland cell acting like “automated switching over” are proposed.     

Genetic studies of serum transferrins of free-ranging rhesus macaques of Cayo Santiago, Macaca mulatta (Zimmerman 1780)

Transferrin phenotypes of plasma from 687 semi-free-ranging Macaca mulatta living on Cayo Santiago, Puerto Rico, were determined by starch-gel electrophoresis and autoradiography. Fifteen phenotypes, homozygous or heterozygous products of six codominant autosomal alleles, were present in the population. The 687 animals, prior to March 1973, were divided into eight troops plus peripheral males. By March 1, 1973 the size of the population was reduced to 333 animals, consisting of four troops plus peripheral males. The distributions of transferrin phenotypes and allele frequencies were determined for the population of 687 animals and for 287 of the March 1973 population of 333 animals. Gametic ratios of 382 offspring of 126 females were enumerated. Statistical tests of homogeneity and equilibrium were applied to the data. The results of these tests suggest that, with only a few exceptions, the Cayo Santiago macaques, although divided into social groups, form a single population, and the results are in accord with behavioral observations. The authors suggest that the data on transferrins provide a good baseline for future genetic and ethological studies of evolutionary processes in a population of nonhuman primates.     

铜尾矿对小麦生长发育和生理功能的影响

通过盆栽实验,分析了铜陵铜尾矿对小麦生长发育和生理功能的影响。结果表明,小麦种子能在铜尾矿上萌发,但发芽率和发芽速率均小于正常土壤中播种的小麦,高比例尾矿抑制小麦的株高,尾矿降低叶绿素含量,但对叶绿素a/b无影响,与对照组相比,尾矿组根系表现为变短变粗,须根数减少,尾矿能增加小麦根和茎叶部分生物量,且能明显提高根冠比,在尾矿胁迫下,小麦叶片的细胞膜透性和游离脯氨酸含量随尾矿比例增加而增大,可作为鉴定植物相对抗性的指标。     

光合膜膜脂双半乳糖二酰基甘油的研究进展

本文综述了光合膜膜脂双半乳糖二酰基甘油(DGDG)的生物合成和生理功能的研究进展。DGDG是光合膜中惟一的双半乳糖脂类,在光合膜的不同膜区均有分布。在高等植物叶绿体中,存在着两条不同的DGDG生物合成途径,即原核合成途径和真核合成途径。原核途径只限于在质体内进行,而真核途径还包括一些在内质网内发生的反应。DGDG在维持光系统Ⅱ捕光色素蛋白复合体的寡聚体结构、调控光系统Ⅱ和光系统Ⅱ核心复合物的放氧活性等方面起着重要作用。     

Biochemical and spectroscopic studies of human melanotransferrin (MTf): electron-paramagnetic resonance evidence for a difference between the iron-binding site of MTf and other transferrins

Melanotransferrin (MTf) is a member of the transferrin (Tf) family of iron (Fe)-binding proteins that was first identified as a cell-surface marker of melanoma. Although MTf has a high-affinity Fe-binding site that is practically identical to that of serum Tf, the protein does not play an essential role in Fe homeostasis and its precise molecular function remains unclear. A Zn(II)-binding motif, distinct from the Fe-binding site, has been proposed in human MTf based on computer modelling studies. However, little is known concerning the interaction of its proposed binding site(s) with metals and the consequences in terms of MTf conformation. For the first time, biochemical and spectroscopic techniques have been used in this study to characterise metal ion-binding to recombinant MTf. Initially, the binding of Fe to MTf was examined using 6M urea gel electrophoresis. Although four different iron-loaded forms were observed with serum Tf, only two forms were found with MTf, the apo-form and the N-monoferric holo-protein, suggesting a single high-affinity site. The presence of a single Fe(III)-binding site was also supported by EPR results which indicated that the Fe(III)-binding characteristics of MTf were unique, but somewhat comparable to the N-lobes of human serum Tf and chicken ovo-Tf. Circular dichroism (CD) analysis indicated that, as for Tf, no changes in secondary structure could be observed upon Fe(III)-binding. The ability of MTf to bind Zn(II) was also investigated using CD which demonstrated that the single high-affinity Fe-binding site was distinct from a potential Zn(II)-binding site.     

传统大豆发酵食品中大豆低聚糖的生理功能研究

大豆低聚糖是大豆中可溶性碳水化合物的总称,在大豆和传统大豆发酵食品中含量丰富。近年研究发现大豆低聚糖在改善肠胃道功能、抗肿瘤、调节血脂等方面具有着重要的生理活性,因此引起了国内外研究人员的广泛关注。大豆低聚糖的研究,不仅能为功能性大豆制品的开发提供理论基础,也能为人们合理的膳食提供参考。本文综述了近年来国内外对大豆低聚糖生理保健机能的研究进展。     

土壤有效硅对大豆生长发育和生理功能的影响

人工调节土壤有效硅含量及盆栽试验,研究土壤有效硅对大豆生长发育和生理功能的影响。结果表明,土壤有效硅含量在55．1～202.8mg·kg^-1范围内,随着土壤有效硅含量的提高,大豆种子萌发过程中蛋白酶和脂肪酶活性升高,淀粉酶活性无显著变化,呼吸速率加快,种子活力升高,萌发速度加快,种子萌发率无显著变化;幼苗生长过程中叶片叶绿素含量无显著变化,光合速率加快,根系活力、硝酸还原酶活力升高,蒸腾强度减弱,水分利用效率和叶含水量升高,抗旱保水能力提高。大豆幼苗含硅量与土壤有效硅含量呈线性正相关趋势(r=0．994)。土壤有效硅含量大于2028mg·kg^-1,生理功能不再显著变化,说明土壤中的硅被大豆吸收后,改善了大豆萌发种子和幼苗的生理功能,使种子萌发和幼苗生长加快。     

Interactions between tissue uptake of lead and iron in normal and iron-deficient rats during development

Environmental lead intoxication, which frequently causes neurological disturbances, and iron deficiency are clinical problems commonly found in children. Also, iron deficiency has been shown to augment lead absorption from the intestine. Hence, there is evidence for an interaction between lead and iron metabolism which could produce changes in lead and iron uptake by the brain and other tissues. These possibilities were investigated using 15-, 21-, and 63-old rats with varying nutritional iron and lead status. Dams were fed diets containing 0 or 3% lead-acetate and 0.2% lead-acetate in the drinking water. After weaning, 0.2% lead-acetate in the drinking water became the sole source of dietary lead. Measurements were made of tissue lead and nonheme iron levels and the uptake of⁵⁹Fe after intravenous injection of transferrin-bound⁵⁹Fe. Iron deficiency was associated with increased intestinal absorption of lead as indicated by blood and kidney lead levels in rats exposed to dietary lead. However, iron deficiency did not increase lead deposition in the brain, and in all rats brain lead levels were relatively low (<0.1 μg/g). Lead concentrations in the liver were below 2 μg/g, whereas kidneys had almost 20 times this concentration. Animals with iron deficiency had lower liver iron levels and had increased brain⁵⁹Fe uptake in comparison to control rats. However, iron levels in brain and kidneys were unaffected by lead intoxication regardless of the animal's iron status.⁵⁹Fe uptake rates were also unaffected by lead, but increased rates of uptake were apparent in iron-deficient rats. Lead did increase liver iron levels in all iron-adequate rats, but iron deficiency had little effect. It is concluded that, compared with other tissues, the blood-brain barrier largely restricts lead uptake by the brain and that the uptake that does occur is unrelated to the iron status of the animal. Also, the level of lead intoxication produced in this investigation did not influence iron uptake by the brain and kidneys, but liver iron stores could be incresed if iron levels were already adequate.     

糜酶的研究进展

糜酶是一类丝氨酸蛋白酶,主要存在于肥大细胞的分泌颗粒和细胞间质。成熟的酶为一糖蛋白,由２２６个氨基酸组成,分子量为３０ｋＤ,其酶活力能被丝氨酸蛋白酶抑制剂所抑制,而不受血管紧张素Ⅰ转换酶抑制剂的影响。糜酶的ｃＤＮＡ和基因组ＤＮＡ均已被克隆和测序。该酶和神经炎症反应、血管活性肽代谢和细胞外基质代谢等有密切联系,在心脏血管紧张素Ⅱ形成中起重要作用。