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排序方式: 共有220条查询结果,搜索用时 15 毫秒
1.
Crystals of the steroid-metabolizing enzyme, delta 5-3-ketosteroid isomerase (EC 5.3.3.1) from Pseudomonas testosteroni, exhibit many enzymatic properties. Each enzyme subunit in the lattice binds a competitive inhibitor, progesterone, with the same stoichiometry (1:1) and affinity (KD = 6 X 10(-6) M) as the enzyme in solution. Another competitive inhibitor, 19-nortestosterone, competes with progesterone for the same binding sites in the crystal. The enzyme crystals catalyze the conversion of delta 5- to delta 4-ketosteroids, but because the enzyme is so efficient, and substrate diffusion into the crystal is so slow, substrate cannot penetrate deeply into the crystal before being converted to product. A general theoretical formulation is presented to account for the effects of substrate diffusion into enzyme crystals of different shapes and sizes. The dependence of apparent mean enzyme activity in steroid isomerase crystals as a function of crystal size is shown to be consistent with this theoretical formulation. These inhibitor binding and catalytic properties suggest that the enzyme is in an active conformation within these crystals. 相似文献
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Cloning of cDNAs for human phosphoribosylpyrophosphate synthetases 1 and 2 and X chromosome localization of PRPS1 and PRPS2 genes 总被引:3,自引:0,他引:3
M A Becker S A Heidler G I Bell S Seino M M Le Beau C A Westbrook W Neuman L J Shapiro T K Mohandas B J Roessler 《Genomics》1990,8(3):555-561
Cloned cDNAs representing the entire, homologous (80%) translated sequences of human phosphoribosylpyrophosphate synthetase (PRS) 1 and PRS 2 cDNAs were utilized as probes to localize the corresponding human PRPS1 and PRPS2 genes, previously reported to be X chromosome linked. PRPS1 and PRPS2 loci mapped to the intervals Xq22-q24 and Xp22.2-p22.3, respectively, using a combination of in situ chromosomal hybridization and human x rodent somatic cell panel genomic DNA hybridization analyses. A PRPS1-related gene or pseudogene (PRPS1L2) was also identified using in situ chromosomal hybridization at 9q33-q34. Human HPRT and PRPS1 loci are not closely linked. Despite marked cDNA and deduced amino acid sequence homology, human PRS 1 and PRS 2 isoforms are encoded by genes widely separated on the X chromosome. 相似文献
4.
Purification and characterization of human T-lymphocyte-derived erythroid-potentiating activity 总被引:9,自引:0,他引:9
C A Westbrook J C Gasson S E Gerber M E Selsted D W Golde 《The Journal of biological chemistry》1984,259(16):9992-9996
The human T-lymphoblast cell line, Mo, secretes a number of lymphokines, including erythroid-potentiating activity (EPA), an important early regulator of erythropoiesis. We report purification of EPA to homogeneity, from serum-free Mo-conditioned medium. Purification was accomplished by sequential concentration, ammonium sulfate precipitation, lentil lectin affinity chromatography, gel filtration, and reverse-phase high-performance liquid chromatography. EPA was assayed by its ability to stimulate the growth of large erythroid colonies (bursts) from normal human peripheral blood. The purified EPA has a molecular weight of 28,000 and appears as a single band when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing or nonreducing conditions. Purified EPA stimulates the growth of both early and late erythroid precursors from human bone marrow, as well as colony formation by the K562 human erythroleukemia cell line. Purified EPA has no colony-stimulating factor activity nor does it appear to be a structural protein of the human T-cell leukemia virus subtype II which infects the Mo cells. 相似文献
5.
The objective of this study was to determine the feasibility of using airborne T3 coliphage as a viral tracer in microbial aerosols. Although T3 coliphage was relatively stable when stored either at temperatures ranging from 21 to 37 C or in the frozen state at -20 C, there was a 2-log loss in infectivity when stored for 72 days at 4 C. Either agitation of stored coliphage suspensions held at 31 C or wide fluctuations in storage temperature produced an increased loss of infectivity. In the airborne state, freshly prepared coliphage and stored coliphage behaved similarly, with survival diminishing as the relative humidity (RH) was lowered. The greatest loss occurred during the first five min following aerosolization. The results showed that only under certain conditions of temperature and relative humidity can T3 coliphage be used as a satisfactory aerosol tracer. 相似文献
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Vladimir Divoky Erol Baysal Reyhan Öner M. Akif Çürük Emmitt L. D. Walker III Karel Indrak Titus H. J. Huisman 《Human genetics》1994,93(1):77-78
We have observed a TC mutation at position +96 of the untranslated region 3 to the terminating codon of the -globin gene in members of two Czech families and one black family. Data from initial studies suggested that this change was the cause of a -thalassemia, but continued analyses have provided convincing evidence that this mutation is a simple polymorphism. 相似文献
8.
O el-Kabbani S V Narayana Y S Babu K M Moore T G Flynn J M Petrash E M Westbrook L J DeLucas C E Bugg 《Journal of molecular biology》1991,218(4):695-698
Large crystals of porcine aldose reductase have been grown from polyethylene glycol solutions. The crystals are triclinic, space-group P1, with a = 81.3 A, b = 85.9 A, c = 56.6 A, alpha = 102.3 degrees, beta = 103.3 degrees and gamma = 79.0 degrees. The crystals grow within ten days to dimensions of 0.6 mm x 0.4 mm x 0.2 mm and diffract to at least 2.5 A. There are four molecules in the unit cell related by a set of three mutually perpendicular non-crystallographic 2-fold axes. 相似文献
9.
Edwin M. Westbrook Paul B. Sigler Helen Berman Jenny P. Glusker Gerard Bunick Ann Benson Paul Talalay 《Journal of molecular biology》1976,103(3):665-667
A monoclinic crystal form (, β= 130.1 °) of Δ5-3-ketosteroid isomerase from Pseudomonas testosteroni (EC 5.3.3.1), grown at pH 7.0, has been characterized. Crystal-density measurements show that the asymmetric unit contains 12 protomers (Mr = 13,394). 相似文献
10.
David S. Goodsell Christine Zardecki Luigi Di Costanzo Jose M. Duarte Brian P. Hudson Irina Persikova Joan Segura Chenghua Shao Maria Voigt John D. Westbrook Jasmine Y. Young Stephen K. Burley 《Protein science : a publication of the Protein Society》2020,29(1):52-65
Analyses of publicly available structural data reveal interesting insights into the impact of the three‐dimensional (3D) structures of protein targets important for discovery of new drugs (e.g., G‐protein‐coupled receptors, voltage‐gated ion channels, ligand‐gated ion channels, transporters, and E3 ubiquitin ligases). The Protein Data Bank (PDB) archive currently holds > 155,000 atomic‐level 3D structures of biomolecules experimentally determined using crystallography, nuclear magnetic resonance spectroscopy, and electron microscopy. The PDB was established in 1971 as the first open‐access, digital‐data resource in biology, and is now managed by the Worldwide PDB partnership (wwPDB; wwPDB.org ). US PDB operations are the responsibility of the Research Collaboratory for Structural Bioinformatics PDB (RCSB PDB). The RCSB PDB serves millions of RCSB.org users worldwide by delivering PDB data integrated with ~40 external biodata resources, providing rich structural views of fundamental biology, biomedicine, and energy sciences. Recently published work showed that the PDB archival holdings facilitated discovery of ~90% of the 210 new drugs approved by the US Food and Drug Administration 2010–2016. We review user‐driven development of RCSB PDB services, examine growth of the PDB archive in terms of size and complexity, and present examples and opportunities for structure‐guided drug discovery for challenging targets (e.g., integral membrane proteins). 相似文献