Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.31.1 (micrococcal nuclease)
 2,818 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects induced by Fe, Mn, or Mg deficiency or cold shock on the DNA content and histones of Euglena gracilis have been examined and compared to those produced by Zn deficiency. The DNA content of the stationary-phase organisms used as controls is 2.1 micrograms/10(6) cells. The DNA of stationary-phase iron-deficient (-Fe), magnesium-deficient (-Mg), manganese-deficient (-Mn), zinc-deficient (-Zn), and cold-shocked (CS) cells is increased to 3.0, 4.6, 6.2, 3.8, and 3.8 micrograms/10(6) cells, respectively. The electrophoretic mobilities of proteins solubilized with 0.4 N H2SO4 from CS, -Fe, -Mg, and -Mn cells are nearly identical and are characteristic of the five histone classes, H1, H2A, H2B, H3, and H4. In contrast, no histones are found in the equivalent acid extract from -Zn cells. The effect of micrococcal nuclease on chromatin from control, CS, and -Zn cells was examined. The chromatin of CS cells is 1.2-fold while that from -Zn cells is 10-30-fold more resistant to micrococcal nuclease digestion than is the chromatin of control cells. Thus, the chromatin of cells grown in Zn-deficient conditions differs markedly from that of organisms cultured in media deficient in Fe, Mn, or Mg or exposed to cold shock.
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PMID:Euglena gracilis chromatin: comparison of effects of zinc, iron, magnesium, or manganese deficiency and cold shock. 309 72

Prions were purified from scrapie-infected hamster brains and incubated for 24 hr at 65 degrees with 2 mM Zn2+ or 5 mM Mg2+; no loss of infectivity was observed. Bacteriophage M13, tobacco mosaic virus (TMV), potato virus X, and potato spindle tuber viroid were all inactivated by divalent metal ions under these conditions. Prions also resisted inactivation by prolonged digestions with DNase I, RNases A and T1, and micrococcal nuclease. Prions were resistant to psoralen photoadduct formation using high concentrations of psoralens; in contrast, M13 bacteriophage was inactivated by low concentrations of all these psoralens. Hydroxylamine failed to inactivate prions even after lengthy exposures to concentrations as high as 1 M, while TMV and M13 were both inactivated. Sonication of prions failed to decrease infectivity even though rod-shaped aggregates were disrupted while both M13 and TMV lost infectivity.
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PMID:Purified scrapie prions resist inactivation by procedures that hydrolyze, modify, or shear nucleic acids. 311 50

Higher-order chromatin structure and the process of transcription are related. The significance of a nutritional state's altering chromatin structure lies in the potential role of that nutritional state in the regulation of gene expression. In rats short-term feeding of semisynthetic diets varying in the proportion of carbohydrate, protein, or fat alters the configuration of liver chromatin as measured by sensitivity to micrococcal nuclease (EC 3.1.31.1). A carbohydrate-rich, fat-free diet increases the sensitivity of rat liver chromatin to micrococcal nuclease and decreases the nucleosome repeat length. In contrast, a protein-free diet or a diet deficient in magnesium or zinc decreases the sensitivity of liver nuclear chromatin to micrococcal nuclease. Diet-mediated mechanisms that alter chromatin structure are now unknown, but the continued study of nutritional interaction with the genome should identify the responsible features as well as their significance to gene function.
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PMID:Diet-mediated alteration of chromatin structure. 352 32

The histone content of zinc-deficient (-Zn) Euglena gracilis decreases while, concomitantly, DNA content increases and the transcription rate is reduced markedly [Mazus, B., Falchuk, K. H., & Vallee, B. L. (1983) Biochemistry (in press); Falchuk, K. H., Fawcett, D. W., & Vallee, B. L. (1975) J. Cell Sci. 17, 57-78]. The effects on major constituents of the genome have been examined by studying the rate and extent of hydrolysis of +Zn and -Zn chromatin by micrococcal nuclease, DNase I, or DNase II. The size of hydrolyzed DNA fragments suggests similarity of the +Zn E. gracilis chromatin organization to that of other eukaryotes. The major protein constituent of -Zn chromatin is a polypeptide of less than 3000 daltons whose electrophoretic mobility differs from that of any known histone components of chromatin, the latter described elsewhere (K. H. Falchuk et al., unpublished results). This protein profoundly affects the structure of -Zn chromatin, which is about 10-30-fold more resistant to micrococcal nuclease hydrolysis than +Zn chromatin. Moreover, the resultant DNA fragments [2000 base pairs (bp)], are much larger than those of +Zn cells. Under conditions which hydrolyze +Zn chromatin into DNA fragments smaller than 50 bp, only 50% of -Zn chromatin is digested into fragments less than 2000 bp, i.e., in the range of those expected for oligonucleosomes. Removal of the low molecular weight protein from -Zn chromatin reverses its enhanced resistance to nucleolysis and results in extensive hydrolysis. Conversely, addition of the low molecular weight protein to +Zn chromatin increases the resistance of this complex to digestion.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Composition and structure of zinc-deficient Euglena gracilis chromatin. 622 50

The phosphodiesterase from calf spleen (EC 3.1.4.18) was immobilized on several supports. Some properties of the most suitable enzyme support system--calf spleen phosphodiesterase bound to agarose-Concanavalin A--were investigated, e.g., pH dependence, influence of ionic strength of the buffer medium, and Zn2+-ion inhibition. The immobilized spleen phosphodiesterase showed about 60% of the activity of the free enzyme; the activity toward several oligonucleotide test substrates was unchanged for two months.
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PMID:Preparation of immobilized phosphodiesterase from calf spleen and its use in oligonucleotide analysis. 624 16

Two types of DNA fragments attached to the nuclear skeleton and protected from staphylococcal nuclease digestion by the nuclear skeleton's proteins were found in Ehrlich ascites carcinoma cells: (i) long (approximately 10 kb) satellite DNA fragments and (ii) short (approximately 140 b. p.) main band DNA fragments. The amount of short DNA fragments depends strongly on the conditions of nuclei isolation. In the preparations obtained from the cells lysed in the medium lacking Cu2+ or Zn2+ short DNA fragments were not found. On the contrary long satellite DNA fragments were found in presumably equal amounts in the nuclei obtained by a wide variety of experimental procedures. Different stability of the structures providing attachment and protection from nuclease digestion of long and short DNA fragments seem to be a good reasons to suggest the existence of two types of attachment points of DNA to the nuclear skeleton.
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PMID:[Two types of attachment points of DNA to the nuclear skeleton in Ehrlich ascites carcinoma cells]. 685 58

Nuclei from frozen calf thymus suspended in buffer were analyzed for metal content prior to and after repeated washing. After three such extractions about 0.1 micrograms Zn/mg DNA and 0.025 micrograms Cu/mg DNA remained tightly associated with chromatin. This level of metal was essentially unchanged with subsequent washings. Digestion of extracted nuclei with micrococcal nuclease yielded soluble nucleoprotein containing zinc and copper. Metal enriched regions of chromatin appeared to be preferentially solubilized by digestion, and the solubilized metal was only partially dializable either with or without EDTA. Metal profiles generated from gel (A-5m) chromatography analysis of chelated and non-chelated solubilized chromatin were distinctive in that copper was undetectable (by flame AA) while zinc was associated only with low molecular weight products when EDTA was used. In contrast, both metals were detected with higher molecular weight oligonucleosomes in the absence of chelating agents. Additionally, the two metals localized within nucleoprotein peaks and these metal-containing regions were only resolved by gel chromatography when EDTA was omitted throughout the procedure. A discrete Cu-rich species in a region of the profile suggests a subset of Cu-rich nucleoprotein complexes.
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PMID:Partitioning of zinc and copper within subnuclear nucleoprotein particles. 731 30

Zinc (Zn) is a trace element in human cells and regarded as an essential nutrient with established deficiency states affecting multiple organs in the body. However, it has been reported that Zn uptake is associated with some serious harmful effects, such as inhibition of DNA synthesis and enhanced toxicity from reactive oxygen species. We have previously shown that in vivo administration of Zn2+ in C57/6J mice induces weight loss and massive hair loss where the normal course hair becomes replaced by fine vello hair, simulating the side effects from cancer chemotherapy where oxidative free radical damage is implicated in association with DNA fragmentation and programmed cell death (PCD). Here, in vitro flow cytometric studies on human Chang liver showed Zn2+ causing cell condensation with DNA fragmentation that occurred in a dose-dependent manner, an effect replicated by micrococcal nuclease digestion. Specific terminal deoxynucleotidyl transferase-(TdT) mediated labeling of 3'-OH ends of DNA nicks corroborated the flow cytometric profiles of propidium iodide-DNA binding where degradation of both 2 and 4 N genomic DNA resulted in a solitary 1N peak presentation. DNA degradation concomitant with cell condensation is seen as an established hallmark of PCD. We further showed that Zn2+ could enhance the generation of hydroxyl free radicals (OH.) by the transition metal vanadium. Glutathione, the cell's main reducing agent, underwent corresponding reduction. The results suggested that Zn supplementation could induce features resembling PCD.
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PMID:Adding Zn2+ induces DNA fragmentation and cell condensation in cultured human Chang liver cells. 936 28

It is shown here that phase diagrams of ligand-binding biological macromolecules provide a powerful tool for the analysis of reaction mechanisms. The present study provides simple rules for the construction and interpretation of such phase diagrams. We give examples for the derivation of reaction schemes for macromolecules that can bind two different kinds of ligands. By sampling one dimension of a phase diagram it is possible to reconstruct the second dimension, including the correct stoichiometry, positive and negative linkage between the ligands and equilibrium binding constants for the complete series of reactions. The discussion is generalised to temperature and pressure-dependent phase diagrams. To exemplify the new diagram method we analyse the pH-dependent binding of trans-beta-indole acrylic acid to apo-Trp repressor, the pH-dependent thermal denaturation of alpha-chymotrypsinogen A, calcium binding and denaturation of annexin I, high affinity zinc binding to a metallo-beta-lactamase and high-pressure and temperature denaturation of RNase A and staphylococcal nuclease.
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PMID:Phase diagrams: a graphical representation of linkage relations. 1268 12

Reverse transcriptase (RT) and integrase (IN) are two key catalytic enzymes encoded by all retroviruses. It has been shown that a specific interaction occurs between the human immunodeficiency virus type 1 (HIV-1) RT and IN proteins (X. Wu, H. Liu, H. Xiao, J. A. Conway, E. Hehl, G. V. Kalpana, V. R. Prasad, and J. C. Kappes, J. Virol. 73:2126-2135, 1999). We have now further examined this interaction to map the binding domains and to determine the effects of interaction on enzyme function. Using recombinant purified proteins, we have found that both a HIV-1 RT heterodimer (p66/p51) and its individual subunits, p51 and p66, are able to bind to HIV-1 IN. An oligomerization-defective mutant of IN, V260E, retained the ability to bind to RT, showing that IN oligomerization may not be required for interaction. Furthermore, we report that the C-terminal domain of IN, but not the N-terminal zinc-binding domain or the catalytic core domain, was able to bind to heterodimeric RT. Deletion analysis to map the IN-binding domain on RT revealed two separate IN-interacting domains: the fingers-palm domain and the carboxy-terminal half of the connection subdomain. The carboxy-terminal domain of IN alone retained its interaction with both the fingers-palm and the connection-RNase H fragments of RT, but not with the half connection-RNase H fragment. This interaction was not bridged by nucleic acids, as shown by micrococcal nuclease treatment of the proteins prior to the binding reaction. The influences of IN and RT on each other's activities were investigated by performing RT processivity and IN-mediated 3' processing and joining reactions in the presence of both proteins. Our results suggest that, while IN had no influence on RT processivity, RT stimulated the IN-mediated strand transfer reaction in a dose-dependent manner up to 155-fold. Thus, a functional interaction between these two viral enzymes may occur during viral replication.
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PMID:Interaction between human immunodeficiency virus type 1 reverse transcriptase and integrase proteins. 1511 87


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