共查询到19条相似文献,搜索用时 125 毫秒
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为研究16bp PUR box中8个完全保守的碱基中的2个碱基在与purR\++阻遏蛋白结合中的功能,对它们分别作了定点突变,使其分别从C,G突变为G,A。凝胶阻滞实验结果表明,含上述保守碱基突变的PUR box均不能与purR\++阻遏蛋白结合。证明这2个保守碱基对维持PUR box的功能是必须的,其中任一改变都导致PUR box功能的丧失。 相似文献
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鼠伤寒沙门氏菌嘌呤生物合成基因表达的调控研究:Ⅱ.O^c突变体的… 总被引:3,自引:3,他引:0
已有研究证明,编码阻遏蛋白的调节基因purR能调节嘌呤从头合成途径中除purB外所有结构基因的表达。但迄今还缺乏阻遏蛋白与这些基因的操作基因相结合的直接证据。本文报道以嘌呤结构基因purD和purG的MudJ插入物为出发株,在外加过量腺嘌呤核苷(2mmol/L)的MacConkey平板上通过选择红色菌落分离O^c突变体的结果,从上述两株出发株分别获得了8株和9株独立的消阻遏突变体。共转导分析和顺反 相似文献
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鼠伤寒沙站氏菌嘌呤生物合成调控研究 总被引:4,自引:1,他引:3
在鼠伤寒沙门氏菌中,由嘌呤从头合成途径合成IMP经10步酶促反应,涉及10个结构基因,其中PurJ purH和purD构成1个操纵子,除purB外均肥反式调节基因purR的负调控。本文以purJHDO^+和O^c突变体为材料,通过体内克隆法分别克隆到O^+purJHK(P2-9)和O^cpurJHD(P^c-12)操纵子;遗传互补和限制性内切酶分析作出了P2-9和P^c-12的物理谱。经2次亚克克 相似文献
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聚乙二醇和金属离子诱导脂质体与细胞的融合 总被引:1,自引:0,他引:1
用荧光菜振能量转移技术检测PEG和金属离子诱导脂质体和细胞的融合,发现有TEG参与诱导时,虽然Ca^2+对膜融合的促进作用仍专一地依赖于PS的存在,但其对PS的依赖性降低;Mn^2+促进含PS和PE的脂质体与细胞的融合,而Mg^2+无作用。以PC:CL:Chol为0.5:0.5:1的脂质体包埋天花粉蛋白,经PEG诱导与骨髓瘤细胞SP20融合,提高了天花粉蛋白对骨髓瘤细胞的杀伤力。 相似文献
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人肝癌细胞的IGF—BP1分子特性及内源性蛋白酶对其降解的研究 总被引:1,自引:0,他引:1
用SDS-PAGE电泳、高效液相色谱(HPLC)、质谱等方法,研究了人肝癌细胞(HepG2)分泌的胰岛素样生长因子结合蛋白-1(^35S-IGF-BP1)的分子结构、特性,及其被内源性蛋白酶降解的特点,^35S-IGF-BP1的经抗体免疫沉淀、生化分离,纯化为均一体,其分子是由多个亚构成的蛋白质,分子量约为27kD;细胞UMR、HepG2、H35BRL3A分泌的蛋白酶能将^35S-IGF-BP1催 相似文献
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二价金属离子Ca^2+、Mg^2+和Mn^2+能增加重组鱼生长激素(brGH)与黑鱼肝膜生长激素受体(GHR)的相互作用,其最适浓度为8-12mmol/L。在这一浓度范围,Ca^2+、Mg^2+和Mn^2+能分别使专一结合提高到无二价阳离子存在时的230%、180%和200%。通过Eadie-Scatchard作图对Ca^2+结合位点进行动态学分析证明brGH-受体复合物存在一个低亲和的Ca^2+ 相似文献
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以超阻遏突变体3—18为出发株,采用以乳糖为唯一碳源的NCE平板的方法分离到439 株调节突变体。通过转导引入tRNA抑制基因从中检测到 11株 purR(am)候选株。共转导分 析证明,这些突变株的琥珀浪突变均发生在purR上。用 supD. supE和 supF分别对上述各amber 突变体作了氨基酸取代实验,初步结果表明:同一氨基酸对purR不同位点(am)的氨基酸取 代,对PurR调节功能有不同程度的影响。不同氨基酸(3种)对purR同一位点(am)的氨基酸取 代,对其调节功能的影响也存在差异。 相似文献
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Salmonella typhimurium 5 phosphoribosylformylglycinamide (FGAR) amidotransferase encoded bypurG gene catalyzes the conversion of FGAR to formylglycinamide ribonucleotide (FGAM) in the presence of glu- tamine and ATP for thede novo purine nucleotide biosynthesis.purG gene is negatively regulated by a repressor-operator system. The O+ purG and Oc purG were cloned respectivelyin vivo. Restriction enzymes analysis of preliminary clones pLBG-1 (O+) and pLBG-2 (Oc) were carried out. The hybrid plasmids pLB1933 (O+) and pLB1927 (Oc) containing 5′ control region ofpurG were constructed and the DNA sequences were determined respectively, DNA sequences data showed that Oc mutation ofpurG occurred at the 3rd position of 16 bp PUR box in the 5′ control region (G→A). Gel retardation experiment indicated that the repressor bound well with O+ PUR box, but not with Oc PUR box. The result strongly supported the idea that PUR box is the binding region of repressor protein and the 3rd position base G of PUR box is essential for the binding function with repressor protein. 相似文献
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Previous work has shown that the carAB operon of Salmonella typhimurium is transcribed from tandem promoters, P1 and P2, that are negatively controlled by pyrimidines and arginine, respectively. The results reported here show that purines also negatively control expression of carAB and that this effect is absent in a purR ::Tn 10 derivative. Primer-extension experiments established that the purine effect is exerted at P1, thus redefining this promoter as sensitive to both purines and pyrimidines. The results of gel-retardation experiments as well as DNase I and premethylation footprintings indicate that the purine repressor interacts with a PUR box 85 bp upstream of P1. Modification of this PUR box by site-directed mutagenesis abolishes the repression by purines in a carA :: lacZ fusion, confirming that this box functions in vivo in purine control of carAB expression. 相似文献
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Salmonella typhimurium 5 phosphoribosylformylglycinamide (FGAR) amidotransferase encoded bypurG gene catalyzes the conversion of FGAR to formylglycinamide ribonucleotide (FGAM) in the presence of glu- tamine and ATP for thede novo purine nucleotide biosynthesis.purG gene is negatively regulated by a repressor-operator system. The O+
purG and Oc
purG were cloned respectivelyin vivo. Restriction enzymes analysis of preliminary clones pLBG-1 (O+) and pLBG-2 (Oc) were carried out. The hybrid plasmids pLB1933 (O+) and pLB1927 (Oc) containing 5′ control region ofpurG were constructed and the DNA sequences were determined respectively, DNA sequences data showed that Oc mutation ofpurG occurred at the 3rd position of 16 bp PUR box in the 5′ control region (G→A). Gel retardation experiment indicated that the
repressor bound well with O+ PUR box, but not with Oc PUR box. The result strongly supported the idea that PUR box is the binding region of repressor protein and the 3rd position
base G of PUR box is essential for the binding function with repressor protein.
Project supported by the National Natural Science Foundation of China. 相似文献
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DnaA protein/DNA interaction. Modulation of the recognition sequence 总被引:13,自引:0,他引:13
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The herpes simplex virus type 1 regulatory protein ICP4 is a sequence specific DNA binding protein which associates with a number of different sites, some of which include the consensus ATCGTCnnnnYCGRC. In order to investigate the involvement in DNA binding of conserved bases within the consensus, we have synthesised a family of mutant oligonucleotides and tested their ability to form a complex with ICP4. We have also compared the binding specificities of bacterially expressed fragments of ICP4 which include the DNA binding domain. Mutation of most (but not all) bases in the proximal part of the consensus greatly reduced binding by ICP4, as did a mutation affecting the distal part. Most (but not all) G residues identified in methylation interference assays were required for efficient binding. While a bacterially expressed ICP4 peptide encompassing amino acid residues 252-523 bound to DNA with a specificity similar to that of the whole protein, a shorter protein (residues 275-523) had a slightly relaxed DNA binding specificity. 相似文献
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DNA-binding activities of the Drosophila melanogaster even-skipped protein are mediated by its homeo domain and influenced by protein context. 总被引:15,自引:3,他引:12
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The homeo box gene even-skipped (eve) encodes a 376-amino-acid protein that binds with high affinity to sequences located near the 5' termini of the eve and en genes. The 5' en sites are A + T rich and contain copies of the 10-base-pair (bp) consensus sequence T-C-A-A-T-T-A-A-A-T. In contrast, the 5' eve sites are G + C rich and contain the 9-bp sequence T-C-A-G-C-A-C-C-G. Among the five different homeo box proteins that have been tested for binding, eve is unique in that it shows virtually equal preference for the A + T-rich 5' en binding sites and the G + C-rich 5' eve sites. Most of the other proteins bind with a relatively higher affinity to the en sites than to the eve sites. In an effort to identify the regions of the eve protein that are responsible for its efficient binding to both classes of recognition sequences, we analyzed the DNA-binding properties of various mutant eve proteins. These studies suggest that the homeo domain of the eve protein is responsible for both binding activities. However, mutations in distant regions of the protein influenced the binding behavior of the eve homeo domain and caused a reduction in binding to the G + C class of recognition sites. We propose that the protein context of the homeo domain can influence its DNA-binding properties. 相似文献