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  • ATP  (5)
  • Drosophila melanogaster  (3)
  • Animals
  • Coleus (cell cultures)
  • METEOROLOGY AND CLIMATOLOGY
  • Springer  (10)
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Keywords
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  • 1
    Electronic Resource
    Electronic Resource
    ATP-sensitive K+ channels in an insulin-secreting cell line are inhibited byd-glyceraldehyde and activated by membrane permeabilization (1986)
    Springer
    The journal of membrane biology 93 (1986), S. 271-279 
    Details
    ISSN: 1432-1424
    Keywords: K+ channel ; ATP ; glyceraldehyde ; RINm5F cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The control of K+ channels in the insulin-secreting cell line RINm5F has been investigated by patch-clamp singlechannel current recording experiments. The unitary current events recorded from cell-attached patches are due to large and small inwardly rectifying ATP-sensitive K+ channels with conductance properties similar to the two channels previously identified in primary cultured rat islet cells (Findlay, I., Dunne, M.J., & Petersen, O. H.J. Membrane Biol. 88:165–172, 1985). Cell permeabilization through brief exposure to 10 μm digitonin or 0.05% saponin (outside the isolated membrane patch area) results in a dramatic increase in current through the cell-attached patch due to opening of many large and small K+-selective channels. These channels are inhibited in a dose-dependent manner by ATP applied to the bath (near-complete inhibition by 5mm ATP). During prolonged ATP exposure (1–5 min) the initial inhibition is followed by partial recovery of channel activity, although further activation does occur when ATP is subsequently removed. From the maximal number of coincident channel openings in the permeabilized cells (in the absence of ATP), it is estimated that there are on average 12 large ATP-sensitive K+ channels per membrane patch, but in the intact cells less than 5% of the membrane patches exhibited three or more coincident K+ channel openings, indicating the degree to which the channels are inhibited in the resting condition by endogenous ATP. Stimulation of RINm5F cells to secrete insulin was carried out by challenging intact cells with 10mm d-glyceraldehyde.d-glyceraldehyde induced depolarization of the membrane from about −70 to −20 mV and evoked a marked reduction in the open-state probability of both the large and small ATP-sensitive channels.d-glyceraldehyde also induced action potentials in a number of cases. All effects of stimulation were largely transient, lasting about 100 sec. The two ATP-sensitive K+ channels are probably responsible for the resting potential and play a crucial role in coupling metabolism to membrane depolarization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871181
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  • 2
    Electronic Resource
    Electronic Resource
    Purification of rosmarinic acid synthase from cell cultures of Coleus blumei Benth (1993)
    Springer
    Planta 191 (1993), S. 18-22 
    Details
    ISSN: 1432-2048
    Keywords: Coleus (cell cultures) ; Hydroxycinnamic acid ester ; Rosmarinic acid ; Rosmarinic acid synthase (purification)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rosmarinic acid synthase from cell cultures of Coleus blumei Benth. was purified to apparent homogeneity by fractionated ammonium sulfate precipitation (60–80% saturation), hydrophobic interaction chromatography, affinity chromatography and gel filtration. This purification procedure resulted in a 225-fold-enriched specific enzyme activity with a yield of 9%. The protein preparation was apparently pure according to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional gel electrophoresis. The apparent molecular mass determined by gel filtration and SDS-PAGE was 77 kDa, indicating that rosmarinic acid synthase is a monomeric enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240891
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  • 3
    Electronic Resource
    Electronic Resource
    Proposed biosynthetic pathway for rosmarinic acid in cell cultures of Coleus blumei Benth (1993)
    Springer
    Planta 189 (1993), S. 10-14 
    Details
    ISSN: 1432-2048
    Keywords: Coleus (cell cultures) ; Hydroxycinnamic acid ester ; Phenylpropanoid metabolism ; Rosmarinic acid (biosynthetic pathway)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A biosynthetic pathway for rosmarinic acid is proposed. This pathway is deduced from studies of the enzymes detectable in preparations from suspension cells of Coleus blumei. Phenylalanine is transformed to 4-coumaroyl-CoA by the enzymes of the general phenylpropanoid pathway: phenylalanine ammonia-lyase (EC 4.3.1.5), cinnamic acid 4-hydroxylase (EC 1.14.13.11) and hydroxycinnamic acid:CoA ligase (EC 6.2.1.12). Tyrosine is metabolized to 4-hydroxyphenyllactate by tyrosine aminotransferase (EC 2.6.1.5) and hydroxyphenylpyruvate reductase. The ester can be formed from 4-coumaroyl-CoA and 4-hydroxyphenyllactate by the catalytic activity of rosmarinic acid synthase with concomitant release of CoA. Microsomal hydroxylase activities introduce the hydroxyl groups at positions 3 and 3′ of the aromatic rings of the ester 4-coumaroyl-4′-hydroxyphenyllactate giving rise to rosmarinic acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201337
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of pyridine nucleotides on the gating of ATP-sensitive potassium channels in insulin-secreting cells (1988)
    Springer
    The journal of membrane biology 102 (1988), S. 205-216 
    Details
    ISSN: 1432-1424
    Keywords: K+ channel ; ATP ; NAD(P) ; NAD(P)H ; RINm5F cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The single-channel current recording technique has been used to study the influences that the pyridine nucleotides NAD, NADH, NADP and NADPH have on the gating of ATP-sensitive K+ channels in an insulin-secreting cell line (RINm5F). The effects of the nucleotides were studied at the intracellular surface using either excised inside-out membrane patches or permeabilized cells. All four pyridine nucleotides were found to evoke similar effects. At low concentrations, 100 μm and less, each promoted channel opening whereas high concentrations, 500 μm and above, evoked channel closure. The degree of K+ channel activation by pyridine nucleotides (low conc.) was found to be similar to that evoked by the same concentrations of ADP or GTP, whereas the degree of K+ channel inhibition (high conc.) was less marked than that evoked by the same concentrations of ATP, and never resulted in refreshment of K+ channels following removal. The effects of NAD, NADH, NADP and NADPH seemed to interact with those of ATP and ADP. In the presence of 1mm ADP and 4mm ATP, 10 to 100 μm concentrations of the pyridine nucleotides could not evoke channel opening, whereas concentrations of 500 μm and above were found to evoke channel closure. In the presence of 2mm ATP and 0.5mm ADP, however, 10 to 100 μm concentrations of the pyridine nucleotides were able to activate K+ channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01925714
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  • 5
    Electronic Resource
    Electronic Resource
    ATP-sensitive inward rectifier and voltage- and calcium-activated K+ channels in cultured pancreatic islet cells (1985)
    Springer
    The journal of membrane biology 88 (1985), S. 165-172 
    Details
    ISSN: 1432-1424
    Keywords: islet ; K+ channels ; ATP ; Ca2+ ; patch-clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary K+ channels in cultured rat pancreatic islet cells have been studied using patch-clamp single-channel recording techniques in cell-attached and excised inside-out and outside-out membrane patches. Three different K+-selective channels have been found. Two inward rectifier K+ channels with slope conductances of about 4 and 17 pS recorded under quasi-physiological cation gradients (Na+ outside, K+ inside) and maximal conductances recorded in symmetrical K+-rich solutions of about 30 and 75 pS, respectively. A voltage- and calcium-activated K− channel was recorded with a slope conductance of about 90 pS under the same conditions and a maximal conductance recorded in symmetrical K+-rich solutions of about 250 pS. Single-channel current recording in the cell-attached conformation revealed a continuous low level of activity in an apparently small number of both the inward rectifier K+ channels. But when membrane patches were excised from the intact cell a much larger number of inward rectifier K+ channels became transiently activated before showing an irreversible decline. In excised patches opening and closing of both the inward rectifier K+ channels were unaffected by voltage, internal Ca2+ or externally applied tetraethyl-ammonium (TEA) but the probability of opening of both inward rectifier K+ channels was reduced by internally applied 1–5mm adenosine-5′-triphosphate (ATP). The large K+ channel was not operational in cell-attached membrane patches, but in excised patches it could be activated at negative membrane potentials by 10−7 to 10−6 m internal Ca2+ and blocked by 5–10mm external TEA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868430
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  • 6
    Electronic Resource
    Electronic Resource
    Interaction of diazoxide, tolbutamide and ATP4− on nucleotide-dependent K+ channels in an insulin-secreting cell line (1987)
    Springer
    The journal of membrane biology 99 (1987), S. 215-224 
    Details
    ISSN: 1432-1424
    Keywords: K+ channel ; ATP ; diazoxide ; tolbutamide ; RINm5F cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The single-channel current recording technique has been used to study the effects of diazoxide, tolbutamide and ATP, separately and combined, on the gating of nucleotide-regulated K+ channels in the insulin-secreting cell line RINm5F. The effects of diazoxide, tolbutamide and ATP4− were studied at the intracellular membrane surface, using, the open-cell membrane patch configuration. Alone diazoxide was found only inconsistently to evoke channel stimulation, 57% of all applications of the drug (72 times in 48 separate patches) having no effect at concentrations between 0.02 and 0.4mm. In the presence of ATP, however, diazoxide consistently evoked channel activation (seen 87 times in 49 patches, 95% of all applications). The interactions of diazoxide and ATP seemed competitive. Stimulation of channels by diazoxide in the presence of 1mm ATP was suppressed if the concentration of ATP was elevated to 2 or 5mm. In solutions in which Mg2+ had been chelated with EDTA, diazoxide failed to activate channels closed by 1mm ATP; however, this was not due to a direct effect on the channels caused by the absence of Mg2+, but could be explained by the enhanced ATP4− concentration after Mg2+ removal. When the total ATP concentration was lowered to give the same [ATP4−] in the absence of Mg2+ to that present in the control experiments, diazoxide was able to evoke full activation. Channel inhibition evoked by tolbutamide, 0.01 to 1.0mm, did not require the presence of either ATP or Mg2+. In the presence of ATP tolbutamide further reduced the number of channel openings. Diazoxide was able to compete with tolbutamide for control of channel activity, an effect that was augmented by the presence of ATP. In the presence of 0.1mm tolbutamide, diazoxide was unable to stimulate channel openings; however, if the dose of tolbutamide was lowered or ATP made available to the inside of the membrane, channel stimulation occurred.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01995702
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  • 7
    Electronic Resource
    Electronic Resource
    The gating of nucleotide-sensitive K+ channels in insulin-secreting cells can be modulated by changes in the ratio ATP4−/ADP3− and by nonhydrolyzable derivatives of both ATP and ADP (1988)
    Springer
    The journal of membrane biology 104 (1988), S. 165-177 
    Details
    ISSN: 1432-1424
    Keywords: K+ channel ; ATP ; ATP4− ; ADP3− ; RINm5F cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The31P-NMR technique has been used to assess the intracellular ratios and concentrations of mobile ATP and ADP and the intracellular pH in an insulin-secreting cell line, RINm5F. The single-channel current-recording technique has been used to investigate the effects of changes in the concentrations of ATP and ADP on the gating of nucleotide-dependent K+ channels. Adding ATP to the membrane inside closes these channels. However, in the continued presence of ATP adding ADP invariably leads to the reactivation of ATP-inhibited K+ channels, even at ATP4−/ADP3− concentration ratios greater than 7∶1. Interactions between ATP4− and ADP3− seem competitive. An increase in the concentration ratio ATP4−/ADP3− consistently evoked a decrease in the open-state probability of K+ channels; conversely a decrease in ATP4−/ADP3− increased the frequency of K+ channel opening events. Channel gating was also influenced by changes in the absolute concentrations of ATP4− and ADP3−, at constant free concentration ratios. ADP-evoked stimulation of ATP-inhibited channels did not result from phosphorylation of the channel, as ADP-β-S, a nonhydrolyzable analog of ADP, not only stimulated but enhanced ADP-induced activation of K+ channels, in the presence of ATP. Similarly, ADP was able to activate K+ channels in the presence of two nonhydrolyzable derivatives of ATP, AMP-PNP and βγmethylene ATP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870928
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  • 8
    Electronic Resource
    Electronic Resource
    Primary structure and functional aspects of the gene coding for the second-largest subunit of RNA polymerase III of Drosophila (1989)
    Springer
    Molecular genetics and genomics 219 (1989), S. 373-380 
    Details
    ISSN: 1617-4623
    Keywords: Drosophila melanogaster ; Evolutionary conservation ; RNA polymerase III ; Second-largest subunit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have cloned and sequenced the gene coding for the second-largest subunit of RNA polymerase III of Drosophila melanogaster (DmRP135). The gene, interrupted by two introns of 62 and 59 bp, respectively, codes for an mRNA of 3.6 kb. As for other housekeeping genes transcription initiates at several sites (between positions −98 and −76) none of which is preceded by a clear TATA sequence. The deduced polypeptide consists of 1129 amino acids with an aggregate molecular weight of 128 kDa. The protein sequence features the same regions of similarity as observed for the corresponding subunits of RNA polymerase II of Drosophila and yeast and the Escherichia coli β subunit. As in the second-largest subunit of RNA polymerase II there is a zinc-binding motif which is absent in the β subunit of E. coli. Antibodies directed against a fusion protein expressing 164 amino acids of the (DmRP135) polypeptide cross-react with the second-largest subunit of RNA polymerase III of yeast and generate a distinct banding pattern on Drosophila polytene chromosomes distinguishable from that obtained with anti-RNA polymerase II antibodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00259609
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  • 9
    Electronic Resource
    Electronic Resource
    The gene upstream of DmRP128 codes for a novel GTP-binding protein of Drosophila melanogaster (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 391-398 
    Details
    ISSN: 1617-4623
    Keywords: Drosophila melanogaster ; RNA polymerase III second-largest subunit ; Upstream gene ; GTP-binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Upstream of the gene coding for the second-largest subunit of RNA polymerase III (DmRP128) we have found another gene (128up), which is transcribed in the same direction as the RNA polymerase gene. The intergenic distance between the 3′ end of 128up mRNA and the 5′ end of DmRP128 mRNA is only about 100 bp. Transcripts of 128up are present at a much higher level than DmRP128 RNA in Drosophila Schneider 2 cells, embryos, and adult flies. Two transcription start points, seven nucleotides apart, are found for 128up compared to multiple scattered starts for DmRP128. Sequence analysis of 128up cDNA reveals that the gene codes for a 41 kDa protein with homology to GTP-binding proteins and matching four of the structural sequence motifs characteristic of the superfamily of GTPases. Bacterially expressed 128up protein fused to maltose-binding protein specifically binds GTP. Sequences closely related to the 128up protein are found in species as distant as Halobacterium, yeast or mouse; the murine protein is 80% identical to 128up. This evolutionary conservation is indicative of an important, but as yet unknown, physiological role. In accordance with the sequence conservation, antibodies against 128up specifically cross-react with mouse 3T3 cells and human Hep2 cells where the subcellular localization of the protein is predominantly perinuclear. We propose that 128up is a member of a novel class of GTP-binding proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00281788
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  • 10
    Electronic Resource
    Electronic Resource
    Identification of the genes coding for the second-largest subunits of RNA polymerases I and III of Drosophila melanogaster (1991)
    Springer
    Molecular genetics and genomics 228 (1991), S. 424-432 
    Details
    ISSN: 1617-4623
    Keywords: Drosophila melanogaster ; RNA polymerase I ; RNA polymerase III ; Second-largest subunits
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have isolated cDNA and genomic clones of Drosophila melanogaster by cross-hybridization with a 658 by fragment of the yeast gene coding for the second-largest subunit of RNA polymerase III (RET1). Determination of the sequence by comparison of genomic and cDNA regions reveals an ORF of 3405 nucleotides which is interrupted in the genomic sequence by an intron of 48 bp. The deduced polypeptide consists of 1135 amino acids with a calculated molecular weight of 128 kDa. The protein sequence shows the same conserved regions of homology as those observed for all the second-largest subunits of RNA polymerases cloned so far. The gene (DmRP128) obviously codes for a second-largest subunit of an RNA polymerase which is different from DmRP140 and DmRP135. We have purified three distinct RNA polymerase activites from D. melanogaster. By using specific RNA polymerase inhibitors in enzyme assays and by comparing their subunit composition we were able to distinguish between RNA polymerase I, II, and III. RNA polymerase preparations of D. melanogaster were blotted and the second-largest subunits were identified with antibodies raised against polypeptides expressed from DmRP128 and DmRP135. Anti-DmRP135 antibodies react strongly with the second-largest subunit of RNA polymerase I but do not react with the respective subunits of RNA polymerase II and III. The second-largest subunit of RNA polymerase III is only recognized by anti-DmRP128. Previously, we have claimed that DmRP135 codes for the second-largest subunit of RNA polymerase III. Based on the new biochemical data reported here we show that DmRP135 codes instead for the second-largest subunit of RNA polymerase I and that DmRP128 corresponds to the equivalent subunit of RNA polymerase III.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260636
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