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21.
Structural Features of Human Monoamine Oxidase A Elucidated from cDNA and Peptide Sequences 总被引:13,自引:5,他引:8
Yun-Pung P. Hsu Walter Weyler Shiuan Chen Katherine B. Sims William B. Rinehart Margot C. Utterback John F. Powell Xandra O. Breakefield 《Journal of neurochemistry》1988,51(4):1321-1324
Monoamine oxidase (MAO), an important enzyme for the degradation of amine neurotransmitters, has been implicated in neuropsychiatric illness. The amino acid sequence for one form of the enzyme, MAO-A, has been deduced from human cDNA clones and verified against proteolytic peptides. The covalent binding site for the flavin adenine dinucleotide (FAD) cofactor is near the C-terminal region. The presence of features characteristic of the ADP-binding fold suggests that the N-terminal region is also involved in the binding of FAD. These cDNAs should facilitate the study of the structure, function, and intracellular targeting of MAO, as well as the analysis of its expression in normal and pathological states. 相似文献
22.
Phloem Mobility of Xenobiotics: II. Bioassay Testing of the Unified Mathematical Model 总被引:1,自引:1,他引:0
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Two bioassays were used to test phloem mobility of selected xenobiotic compounds: (a) excised bean leaf assay; (b) rooted bean leaf assay. Compounds assayed were N-alkylpyridiniums with systematic variation in octanol-water partition coefficients (log Kow), substituted benzoic acids with about the same log Kow value but variable acidities. Results of the assays strongly conform, quantitatively, to the predictions of the unified mathematical model. Results also indicate that the membrane permeability value of a compound, which depends directly on log Kow value, is the overriding factor in determining phloem mobility. When the weak acid functionality of a compound confers increased phloem mobility, it does so principally by making the log Kow value, and consequently the membrane permeability of the compound more optimal. 相似文献
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24.
Ellipticine increases the superhelical density of intracellular SV40 DNA by intercalation.
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We investigated the in vivo effect of ellipticine, a mammalian topoisomeraseII(topoII) inhibitor, on SV40 DNA topology. In contrast to epipodophyllotoxins, ellipticine did not cause significant double stranded cleavage of intracellular SV40 DNA. Furthermore, ellipticine reduced cleavage induced by epipodophyllotoxins, VP16 and VM26. Unexpectedly, ellipticine dramatically increased the superhelical density of a fraction of intracellular SV40 DNA. Several lines of evidence suggest that the formation of this highly supercoiled DNA species (Ih form DNA) is not due to the inhibition of topoII per se, but is the result of intercalation by ellipticine in a subfraction of the intracellular SV40 chromatin followed by the fixation of DNA linking number by a topoisomerase activity. Based on the linking number change and the known unwinding angle of ellipticine, the intercalation density was calculated as one ellipticine molecule per 10-20 bp in the Ih DNA. This result suggests the existence of different populations of intracellular SV40 chromatin with respect to the accessibility to ellipticine intercalation. 相似文献
25.
Carrier detection and prenatal diagnosis of alpha-thalassemia of Southeast Asian deletion by polymerase chain reaction 总被引:7,自引:0,他引:7
Summary Alpha-thalassemia of Southeast Asian deletion (-- SEA/) is very common in Southeast Asia. Homozygosity of this genotype is the major cause of Hb Bart's hydrops fetalis in Taiwan. With polymerase chain reaction using three oligonucleotide primers bridging the common deletion breakpoint, a DNA fragment of 194 basepairs (bp) was amplified in chromosomes with the-- SEA determinant and a DNA fragment of 287 bp was amplified in chromosomes without this deletion. In our pilot study including 8 normal subjects, 20 obligate carriers, and 11 homozygotes of the deletion, all the genotypes were determined and then confirmed by Southern blotting and DNA hybridization with globin gene probe. For prenatal diagnosis, 55 at-risk pregnancies were collected. Chorionic villus sampling was done in 51 cases and early amniocentesis was done in 4 cases. Fourteen cases (25.5%) were diagnosed as normal, 25 (45.5%) as heterozygotes, and 16 (29%) as homozygotes of -- SEA. All of the diagnoses were also confirmed as aforementioned. With polymerase chain reaction, the determination of the -- SEA deletion is straightforward and is much quicker and easier than with conventional Southern blotting and DNA hybridization. In areas with a high prevalence of -- SEA deletion, this method provides a rapid tool for carrier detection and prenatal diagnosis. 相似文献
26.
X-ray crystal structures of the oxidized and reduced forms of the rubredoxin from the marine hyperthermophilic archaebacterium Pyrococcus furiosus. 总被引:10,自引:8,他引:2
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M. W. Day B. T. Hsu L. Joshua-Tor J. B. Park Z. H. Zhou M. W. Adams D. C. Rees 《Protein science : a publication of the Protein Society》1992,1(11):1494-1507
The structures of the oxidized and reduced forms of the rubredoxin from the archaebacterium, Pyrococcus furiosus, an organism that grows optimally at 100 degrees C, have been determined by X-ray crystallography to a resolution of 1.8 A. Crystals of this rubredoxin grow in space group P2(1)2(1)2(1) with room temperature cell dimensions a = 34.6 A, b = 35.5 A, and c = 44.4 A. Initial phases were determined by the method of molecular replacement using the oxidized form of the rubredoxin from the mesophilic eubacterium, Clostridium pasteurianum, as a starting model. The oxidized and reduced models of P. furiosus rubredoxin each contain 414 nonhydrogen protein atoms comprising 53 residues. The model of the oxidized form contains 61 solvent H2O oxygen atoms and has been refined with X-PLOR and TNT to a final R = 0.178 with root mean square (rms) deviations from ideality in bond distances and bond angles of 0.014 A and 2.06 degrees, respectively. The model of the reduced form contains 37 solvent H2O oxygen atoms and has been refined to R = 0.193 with rms deviations from ideality in bond lengths of 0.012 A and in bond angles of 1.95 degrees. The overall structure of P. furiosus rubredoxin is similar to the structures of mesophilic rubredoxins, with the exception of a more extensive hydrogen-bonding network in the beta-sheet region and multiple electrostatic interactions (salt bridge, hydrogen bonds) of the Glu 14 side chain with groups on three other residues (the amino-terminal nitrogen of Ala 1; the indole nitrogen of Trp 3; and the amide nitrogen group of Phe 29). The influence of these and other features upon the thermostability of the P. furiosus protein is discussed. 相似文献
27.
The immediate-early growth response in regenerating liver and insulin-stimulated H-35 cells: comparison with serum-stimulated 3T3 cells and identification of 41 novel immediate-early genes. 总被引:30,自引:8,他引:22
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K L Mohn T M Laz J C Hsu A E Melby R Bravo R Taub 《Molecular and cellular biology》1991,11(1):381-390
Liver regeneration provides a unique system for analysis of mitogenesis in intact, fully developed animals. Cellular immediate-early genes likely play an important role in cell cycle regulation and have been extensively studied in mitogen-stimulated fibroblasts lymphocytes but not in liver. We have begun to characterize the immediate-early growth response genes of mitogen-stimulated liver cells, specifically, regenerating liver and insulin-stimulated Reuber H-35 hepatoma cells, and to address differences in growth response between different cell types. Through subtraction and differential screening of cDNA libraries from regenerating liver and insulin-treated H-35 cells, we have extensively characterized 341 differentially expressed clones and identified 52 immediate-early genes. These genes have been partially sequenced and subjected to Northern (RNA) blot analysis, and 41 appear to be novel. Surprisingly, two-thirds of these genes are also expressed in BALB/c 3T3 cells, but only 10 were identified in previous studies of 3T3 cells, and of these, 6 include well-known genes like jun and fos, and only 4 are novel. Approximately one-third of the immediate-early genes identified in mitogen-stimulated liver cells or serum-stimulated NIH 3T3 cells are expressed in a tissue-specific fashion, indicating that cell type-specific regulation of the proliferative response occurs during the immediate-early period. Our findings indicate that the immediate-early response is unusually complex for the first step in a regulatory cascade, suggesting that multiple pathways must be activated. The abundance of immediate-early genes and the highly varied pattern of their expression in different cell types suggest that the tissue specificity of the proliferative response arises from the particular set of these genes expressed in a given tissue. 相似文献
28.
29.
Representative facultative anaerobes of the bacterial flora from the intestine of female Ascaris suum were isolated and identified. The number of bacteria in the intestine was approximately 4 X 10(9) per g wet weight of intestine. Seventeen of 19 of the isolated colonies were found to secrete 5-hydroxytryptamine in culture. Holding A. suum in an antibiotic-containing medium did not affect the levels of 5-hydroxytryptamine in the worm, which were 231 +/- 14 ng/g in antibiotic-media as compared to 250 +/- 16 ng/g in control media. This implied that the bacteria may not be contributing to the level of 5-hydroxytryptamine in the tissues of A. suum. 相似文献
30.
Mitotic inhibition and aneuploidy induction by naturally occurring and synthetic estrogens in Chinese hamster cells in vitro 总被引:2,自引:0,他引:2
We used a predominantly diploid Chinese hamster cell line to test a number of naturally occurring and synthetic estrogens for their ability to arrest cells at metaphase, their potential for allowing anaphase recovery, and their capability of inducing aneuploid progeny. The chemicals employed included diethylstilbestrol, dienestrol, hexestrol, beta-estradiol, ethynylestradiol and estriol. We also tested progesterone, estrone and testosterone in this regard. Only estrogens and their synthetic analogs caused mitotic arrest and aneuploidy, while progesterone, estrone and testosterone did not cause mitotic disturbances. Among the estrogens, DES was the most effective arrestant on a comparative molar basis, whereas dienestrol was most potent over a wide range of concentrations. Estriol was the least potent as an arrestant but was an effective inducer of aneuploidy. The addition of a metabolic activator (S9) did not alter the ability of DES to arrest mitosis. Following the removal of the drugs, cells were able to quickly reorganize a spindle apparatus and enter anaphase. Diethylstilbestrol, dienestrol, hexestrol, beta-estradiol, ethynylestradiol and estriol caused significant increase in aneuploidy within a narrow range of high concentrations in recovering cell populations. Aneuploidy was induced in a non-random manner. Immunofluorescence studies with anti-tubulin antibody indicate that estrogens may have a mechanism of mitotic arrest similar to that of colchicine and colcemid, viz inhibiting the polymerization of tubulin to form microtubules. These data suggest that the interaction between estrogens and microtubules may mediate the induction of aneuploidy in somatic cells. Aneuploidy induction by DES and similar compounds may be related to their carcinogenic potential. 相似文献