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1.
Thermoplasma acidophilum is a thermoacidophilic archaebacterium occupying a paradoxical place in phylogenetic trees (phenotypically it is a thermoacidophile but phylogenetically it classifies with the methanogens). To better understand its phylogeny, the pyruvate kinase from this organism is being investigated as a molecular marker. The enzyme has been purified and has a native M(r) of 250,000. It consists of four, apparently identical subunits each of M(r) 60,000. No remarkable kinetic differences have been found between this thermophilic enzyme and its mesophilic counterparts other than its greater thermostability. Its amino acid composition has been determined and some partial sequencing has been done. 相似文献
2.
Three series of bitobic arylpiperazine-phenyl-hexahydropyrazinoquino- lines analogues were designed, synthesizedand evaluated as a novel class of selective ligands for the dopamine D3 receptor. Compounds 15a (Ki of 11.7 ± 1.8 and 373 nM at D3 and D2, respectively), 15c (Ki of 5.49 and 264 nM at D3 and D2, respectively), 15e (Ki of 14.9 and 325 nM at D3 and D2, respectively), 15i (Ki of 13.8 and 401 nM at D3 and D2, respectively) and 15l (Ki of 13.6 and 870 nM at D3 and D2, respectively) were found to demonstrate good binding affinity and selectivity, and especially compound 15c showeda similar binding affinity and selectivity compared with the contrast drug BP897. 相似文献
3.
人睫状神经营养因子的原核表达,纯化及其生物效应 总被引:2,自引:0,他引:2
人睫状神经营养因子(hCNTF)克隆入pBV220中,在DH5α菌株中表达,重组蛋白以包含体的形式存在,表达量为菌体总蛋白的50%左右。经比较发现用2mol/L脲洗涤包含体可溶解大量可溶性细菌蛋白,且包含体损失较小。在高浓度变性剂条件下进行sepharcylS-200凝胶过滤,解决了纯化中hCNTF易聚合的问题,在低浓度变性剂条件下进行DEAE离子交换,有利于蛋白活性的保持。经两步纯化后得到均一性hCNTF,纯度达95%以上。在自然状态下使hCNTF复性。纯化复性后的hCNTF对无血清培养的鸡胚背根节神经元和脊髓腹角运动神经元有明显的维持存活和促进生长发育的生物效应。 相似文献
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《Cell》2021,184(24):5970-5984.e18
7.
《Journal of molecular biology》2021,433(9):166910
The Smc5/6 complex facilitates chromosome replication and DNA break repair. Within this complex, a subcomplex composed of Nse1, Nse3 and Nse4 is thought to play multiple roles through DNA binding and regulating ATP-dependent activities of the complex. However, how the Nse1-Nse3-Nse4 subcomplex carries out these multiple functions remain unclear. To address this question, we determine the crystal structure of the Xenopus laevis Nse1-Nse3-Nse4 subcomplex at 1.7 Å resolution and examine how it interacts with DNA. Our structural analyses show that the Nse1-Nse3 dimer adopts a closed conformation and forms three interfaces with a segment of Nse4, forcing it into a Z-shaped conformation. The Nse1-Nse3-Nse4 structure provides an explanation for how the lung disease immunodeficiency and chromosome breakage syndrome-causing mutations could dislodge Nse4 from Nse1-Nse3. Our DNA binding and mutational analyses reveal that the N-terminal and the middle region of Nse4 contribute to DNA interaction and cell viability. Integrating our data with previous crosslink mass spectrometry data, we propose potential roles of the Nse1-Nse3-Nse4 complex in binding DNA within the Smc5/6 complex. 相似文献
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Two novel type I casein kinases named CK-1B and CK-1C have been purified from maize endosperm (three weeks after anthesis) by a six step procedure involving ammonium sulfate precipitation, DEAE-cellulose, Sephadex G-75, Heparin-sepharose, and ATP-agarose chromatography. The catalytic subunits of both enzymes were identified as a 35-37 kDa polypeptide doublet by in situ phosphorylation after SDS/PAGE in active casein gel. Both enzymes required 5-10 mmol · L−1 Mg2+ for maximal activity, could utilize only ATP as phosphate donor, were insensitive to heparin, were not autophosphorylated, had a pH optimum at pH 7 to 8.5, and exclusively phosphorylated acidic proteins (casein, phosvitin). Regarding the enzyme differences, their properties were as follows: a) CK-1B could bind on ATP-agarose affinity column, while CK-1C could not; b) the activity of CK-1C was strongly stimulated at low concentrations (1 mmol/L) of spermine, while that of CK-1B was inhibited; c) CK-1B and CK-1C Km values for ATP were 11 μmol · L−1 and 26 μmol · L−1, respectively; d) Mg2+ could substituted by Mn2+ in the CK-1B catalytic activity (by about 80 percnt;); e) CK-1B phosphorylated serine, while CK-1C both serine and threonine on casein. The combination of these results with those from Babatsikos and Yupsanis (2000) brings the number of investigated maize endosperm CK-I isoforms to three (CK-1B, CK-1C, and CK-1E). This is the first biochemical approach demonstrating that multiple isoforms of CK-I casein kinases are present in the same plant tissue. 相似文献
10.
Charles W. Francis Elizabeth M. Keele Victor J. Marder 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,797(3):328-335
Three forms of the normal human plasma fibrinogen γ-chain which differ in molecular weight have been purified. Plasma fibrinogen was separated by ion exchange chromatography on DEAE-Sephacel into three populations of molecules, each with a unique γ-chain composition. Following reduction and S-carboxymethylation, the fibrinogen polypeptide chains in each chromatographic peak were separated by ion exchange chromatography on DEAE-Sephacel and identified following sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The Aα, Bβ and smallest γ-chain (γ50) eluted at progressively higher ionic strengths, but the elution positions of Aα, Bβ and γ50 chains were identifcal for fibrinogen from each of the three different chromatographic fractions. The unique γ chain of fibrinogen in the second chromatographic peak (γ55) eluted at an ionic strength higher than that of the γ50 chain, while the largest γ-chain (γ57.5), which was contained only in the third chromatographic peak of fibrinogen, eluted at the highest ionic strength. The higher ionic strengths needed to elute fibrinogen in the second and third peaks was paralleled by the higher ionic strengths needed to elute the γ-chains unique to them, suggesting that the γ-chain composition of the three fibrinogen fractions accounted for their differential binding to the ion exchange resin. Following desialation with neuraminidase, the differences in electrophoretic mobilities between the three γ-chain forms was maintained, indicating that differential migration on SDS-polyacrylamide gel electrophoresis was not due to variation in sialic acid content. 相似文献