scholarly journals STUDIES ON NUCLEAR STRUCTURE AND FUNCTION IN TETRAHYMENA PYRIFORMIS

1969 ◽  
Vol 42 (3) ◽  
pp. 673-682 ◽  
Author(s):  
Martin A. Gorovsky ◽  
John Woodard
Keyword(s):  
Cell Cycle ◽  
Rna Synthesis ◽  
Specific Activity ◽  
Tetrahymena Pyriformis ◽  
Small Population ◽  
Structure And Function ◽  
Camera Lucida ◽  
Frequency Distributions ◽  
And Function ◽  
Growth And Reproduction

Tetrahymena in the log phase of growth were pulse labeled with uridine-3H, fixed in acetic-alcohol, extracted with DNase, and embedded in Epon. 0.5-µ sections were cut, coated with Kodak NTB-2 emulsion, and developed after suitable exposures. Grains were counted above macronuclei, above 1000 micronuclei, and above 1000 micronucleus-sized "blanks" which were situated next to micronuclei in the visual field by means of a camera lucida. An analysis of grain counts showed that micronuclei were less than ½000 as active as macronuclei on the basis of grains per nucleus. Since micronuclei contained, on the average, about ½0 as much DNA as macronuclei, micronuclear DNA had less than 1% of the specific activity of macronuclear DNA in RNA synthesis. However, even this small amount of apparent incorporation was not significantly different from zero. Comparisons of the frequency distributions of labeled micronuclei with those of micronuclear "blanks" showed no evidence of a small population of labeled nuclei such as might be expected if micronuclei synthesized RNA for only a brief portion of the cell cycle. We conclude from these studies that there is no detectable RNA synthesis in Tetrahymena micronuclei during vegetative growth and reproduction.

scholarly journals Micro-analysis of pure deoxyribonucleic acid-dependent ribonucleic acid polymerase from Escherichia coli. Action of heparin and rifampicin on structure and function

1970 ◽  
Vol 117 (3) ◽  
pp. 623-631 ◽  
Author(s):  
Volker Neuhoff ◽  
Wolf-Bernhard Schill ◽  
Hans Sternbach
Keyword(s):  
Escherichia Coli ◽  
Rna Polymerase ◽  
Rna Synthesis ◽  
Deoxyribonucleic Acid ◽  
Structure And Function ◽  
Disc Electrophoresis ◽  
Inhibitory Mechanism ◽  
And Function ◽  
Micro Analysis ◽  
Template Complex

By using micro disc electrophoresis and micro-diffusion techniques, the interaction of pure DNA-dependent RNA polymerase (EC 2.7.7.6) from Escherichia coli with the template, the substrates and the inhibitors heparin and rifampicin was investigated. The following findings were obtained: (1) heparin converts the 24S and 18S particles of the polymerase into the 13S form; (2) heparin inhibits RNA synthesis by dissociating the enzyme–template complex; (3) rifampicin does not affect the attachment of heparin to the enzyme; (4) the substrates ATP and UTP are bound by enzyme loaded with rifampicin; (5) rifampicin is bound by an enzyme–template complex to the same extent as by an RNA-synthesizing enzyme–template complex. From this it is concluded that the mechanism of the inhibition of RNA synthesis by rifampicin is radically different from that by heparin. As a working hypothesis to explain the inhibitory mechanism of rifampicin, it is assumed that it becomes very firmly attached to a position close to the synthesizing site and only blocks this when no synthesis is in progress.

scholarly journals The essential activities of the bacterial sigma factor

2017 ◽  
Vol 63 (2) ◽  
pp. 89-99 ◽  
Author(s):  
Maria C. Davis ◽  
Christopher A. Kesthely ◽  
Emily A. Franklin ◽  
Shawn R. MacLellan
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Rna Synthesis ◽  
Gene Expression Regulation ◽  
Structure And Function ◽  
Structural Studies ◽  
General Transcription Factors ◽  
Transcription Process ◽  
Promoter Dna ◽  
And Function

Transcription is the first and most heavily regulated step in gene expression. Sigma (σ) factors are general transcription factors that reversibly bind RNA polymerase (RNAP) and mediate transcription of all genes in bacteria. σ Factors play 3 major roles in the RNA synthesis initiation process: they (i) target RNAP holoenzyme to specific promoters, (ii) melt a region of double-stranded promoter DNA and stabilize it as a single-stranded open complex, and (iii) interact with other DNA-binding transcription factors to contribute complexity to gene expression regulation schemes. Recent structural studies have demonstrated that when σ factors bind promoter DNA, they capture 1 or more nucleotides that are flipped out of the helical DNA stack and this stabilizes the promoter open-complex intermediate that is required for the initiation of RNA synthesis. This review describes the structure and function of the σ70 family of σ proteins and the essential roles they play in the transcription process.

Review: The Dynamics of the Nuclear Lamins during the Cell Cycle— Relationship between Structure and Function

2000 ◽  
Vol 129 (2-3) ◽  
pp. 324-334 ◽  
Author(s):  
Robert D. Moir ◽  
Timothy P. Spann ◽  
Reynold I. Lopez-Soler ◽  
Miri Yoon ◽  
Anne E. Goldman ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Structure And Function ◽  
Nuclear Lamins ◽  
And Function

scholarly journals The Modular Structure and Function of the Wheat H1 Promoter with S Phase-Specific Activity

1998 ◽  
Vol 39 (3) ◽  
pp. 294-306 ◽  
Author(s):  
K.-i. Taoka ◽  
N. Ohtsubo ◽  
Y. Fujimoto ◽  
K. Mikami ◽  
T. Meshi ◽  
...  
Keyword(s):  
Specific Activity ◽  
Structure And Function ◽  
S Phase ◽  
Modular Structure ◽  
And Function

Ecological role of grapsid crabs in mangrove ecosystems: a review

1998 ◽  
Vol 49 (4) ◽  
pp. 335 ◽  
Author(s):  
S. Y. Lee
Keyword(s):  
Organic Matter ◽  
Structure And Function ◽  
Mangrove Species ◽  
Organic Matter Production ◽  
Mangrove Ecosystems ◽  
Matter Production ◽  
Feeding Activities ◽  
And Function ◽  
Growth And Reproduction

Recent research on Indo–Pacific mangroves has confirmed the significant role played by grapsid crabs in the structure and function of these ecosystems. Through the feeding activities of the crabs, large proportions of organic matter production, i.e. mangrove leaves, are recycled within the forest. This initial retention of production in the forest refines earlier estimates of tidal export from the mangroves. Crab-processed organic matter could also form the basis of a coprophagous food chain involving small invertebrates, or be re-exported as micro-particulates. Differential consumption by crabs of mangrove propagules also affects mangrove community structure by diminishing the relative abundance of species whose propagules are preferred foods. Bioturbation by the crabs also results in changes in surface topography, particle size distribution and degree of aeration and, thus, the concentration of phytotoxins in the substratum. Such changes could affect growth and production of the mangroves. Growth and reproduction of the crabs may in turn be influenced by the associated mangrove species, mainly through the provision of food. The semi-terrestrial and air-breathing habit of the grapsid crabs probably makes them tolerant of deoxygenation caused by organic enrichment, but development of the landward mangroves will strongly affect survival of the crabs.

scholarly journals Preservation of the native structure and function of Ca2+-ATPase from sarcoplasmic reticulum: Solubilization and reconstitution by new short-chain phospholipid detergent 1,2-diheptanoyl-sn-phosphatidylcholine

1997 ◽  
Vol 325 (2) ◽  
pp. 533-542 ◽  
Author(s):  
Bannikuppe D. SHIVANNA ◽  
Elizabeth S. ROWE
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Membrane Proteins ◽  
Conformational Transition ◽  
Specific Activity ◽  
Structure And Function ◽  
Native Structure ◽  
Lipid Interactions ◽  
Lauryl Ether ◽  
And Function

The properties of Ca2+-ATPase purified and reconstituted from rabbit skeletal sarcoplasmic reticulum (SR) has been studied in comparison with the preparations obtained by the commonly used detergent poly(oxyethylene)8-lauryl ether (C12E8) and the bile salt detergents cholate and deoxycholate. 1,2-Diheptanoyl-sn-phosphatidylcholine (DHPC) has been shown to be excellent for solubilizing a wide variety of membrane proteins [Kessi, Poiree, Wehrli, Bachofen, Semenza and Hauser (1994) Biochemistry 33, 10825–10836]. The DHPC method consistently gave higher yields of purified Ca2+-ATPase with a greater specific activity than the methods with C12E8, cholate, or deoxycholate. DHPC and C12E8 were superior to cholate and deoxycholate in active enzyme yields and specific activity. DHPC-solubilized Ca2+-ATPase purified on a density gradient retained the E1Ca–E1*Ca conformational transition, whereas the enzyme from the C12E8 purification did not retain this transition. The coupling of Ca2+ transported to ATP hydrolysed in the DHPC-purified enzyme was maximal and matched the values obtained with native SR, whereas the coupling was much lower for the C12E8-purified enzyme. The specific activity of Ca2+-ATPase reconstituted into dioleoylphosphatidylcholine vesicles with DHPC was up to 2-fold greater than that achieved with C12E8, and is comparable to that measured in the native SR. Finally, the dissociation of Ca2+-ATPase into monomers by DHPC preserved the ATPase activity, whereas similar dissociation by C12E8 gave only one-sixth the activity of that obtained with DHPC. These studies show that the Ca2+-ATPase solubilized, purified and reconstituted with DHPC is superior to that obtained with C12E8 in significant ways, making it a preparation suitable for detailed studies on the mechanism of ion transport and the role of protein–lipid interactions in the function of membrane proteins.

THE EFFECT OF IONS ON THE STRUCTURE AND FUNCTION OF FACULTATIVE HETEROCHROMATIN IN THE MEALY BUG

1972 ◽  
Vol 14 (4) ◽  
pp. 809-815 ◽  
Author(s):  
Dominick Pallotta
Keyword(s):  
Ionic Strength ◽  
Rna Synthesis ◽  
Large Mass ◽  
Structure And Function ◽  
Hypotonic Solution ◽  
Isotonic Solution ◽  
Salt Solutions ◽  
Facultative Heterochromatin ◽  
Mealy Bug ◽  
And Function

When mealy bug testis cells are placed in an isotonic salt solution, a large mass of heterochromatic chromosomes is visible. As the ionic strength is lowered, these chromosomes decondense and can no longer be distinguished from the euchromatic chromosomes. This change is reversed by returning the cells to isotonic medium. Labeling experiments showed that this recondensation process is specific in the sense that it is the original heterochromatic chromosomes which recondense. In isotonic salt solutions, the heterochromatic chromosomes synthesize little or no RNA as compared to the euchromatic chromosomes. In hypotonic solution, cells show a general decrease in RNA synthesis, but they exhibit the same pattern of RNA synthesis as cells in isotonic solution. Therefore, it is concluded that this ion-mediated decondensation of chromosomes does not increase their capacity to synthesize RNA.

The influence of chronic ethanol feeding to rats on liver mitochondrial membrane structure and function

1980 ◽  
Vol 58 (10) ◽  
pp. 1147-1155 ◽  
Author(s):  
E. A. Hosein ◽  
Hung Lee ◽  
Ilan Hofmann
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Rat Liver ◽  
Mitochondrial Membrane ◽  
Membrane Structure ◽  
Membrane Lipids ◽  
Specific Activity ◽  
Structure And Function ◽  
Membrane Structure And Function ◽  
And Function

Arrhenius plots were generated on the activity of rat liver mitochondrial cytochrome c oxidase from Metrecal–sucrose fed controls and Metrecal–alcohol fed experimentals. Chronic alcohol feeding resulted in diminished specific activity of cytochrome c oxidase and abolition of the discontinuity temperature at 17.5 °C found in the controls. Twenty-four hours after alcohol withdrawal, a discontinuity temperature reappeared at 14.4 °C; at 48 h it increased to 22.6 °C and returned to normal (17.4 °C) at 72 h. Such liver mitochondria also showed a decreased capacity to oxidize the acetyl group of acetyl carnitine immediately following prolonged alcohol feeding. When the assay was performed following withdrawal from alcohol 24 h later, oxidation was enhanced and this effect persisted for another 48 h. These latter results revealed a diminished capacity of such mitochondria to oxidize short chain fatty acids during alcohol feeding and the reverse during alcohol withdrawal.These results, complemented by thermographic data obtained through differential scanning calorimetry (DSC) reinforced the view that chronic alcoholic feeding induced adaptive changes in the fluidity of rat liver mitochondrial membrane lipids. Moreover, they demonstrated that in the microenvironment of the membrane-bound enzymes on withdrawal from ethanol, the membrane readapts to the new conditions without alcohol. This involved modulation of membrane structure and function and at the same time demonstrated a role for the membrane in the expression of tolerance and functional dependence on alcohol.

scholarly journals STUDIES ON NUCLEAR STRUCTURE AND FUNCTION IN TETRAHYMENA PYRIFORMIS

1970 ◽  
Vol 47 (3) ◽  
pp. 631-636 ◽  
Author(s):  
Martin A. Gorovsky
Keyword(s):  
Nuclear Structure ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Tetrahymena Pyriformis ◽  
Structure And Function ◽  
Polyacrylamide Gel ◽  
And Function

Histones were extracted from isolated macro- and micronuclear fractions and from nucleohistone fibers which were prepared from the isolated macronuclear fraction. Analysis of these histones by polyacrylamide gel electrophoresis indicated that there are electrophoretic differences between the histones of macro- and micronuclei.

Sign in / Sign up

Export Citation Format

Share Document