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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 16 (1994), S. 13-22 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: DNA helicases catalyze the disruption of the hydrogen bonds that hold the two strands of double-stranded DNA together. This energy-requiring unwinding reaction results in the formation of the single-stranded DNA required as a template or reaction intermediate in DNA replication, repair and recombination. A combination of biochemical and genetic studies have been used to probe and define the roles of the multiple DNA helicases found in E. coli. This work and similar efforts in eukaryotic cells, although far from complete, have established that DNA helicases are essential components of the machinery that interacts with the DNA molecule.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 13 (1997), S. 1465-1475 
    ISSN: 0749-503X
    Keywords: HEL1 ; scHelI ; yeast helicases ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The gene encoding scHelI, a previously characterized DNA helicase from Saccharomyces cerevisiae, has been identified as YER176w, an open reading frame on chromosome V. The gene has been named HEL1 to indicate the DNA helicase activity of the gene product. HEL1 was identified by screening a |glgt11 yeast protein expression library with antiserum to purified scHelI. Several independent immunopositive clones were isolated and shown to contain portions of HEL1 either by sequencing or by hybridization to a probe containing HEL1 sequences. The HEL1 open reading frame includes the seven conserved helicase motifs, consistent with the DNA helicase activity of scHelI, and the predicted size of the protein is in agreement with the size of purified scHelI. Partially purified cellular extracts from a hel1 deletion mutant strain did not contain scHelI activity. Homology searches revealed protein sequence homology between HEL1 and two previously identified and biochemically characterized yeast helicases, encoded by the DNA2 and UPF1 genes.Haploid hel1 deletion strains were constructed and shown to be viable with growth rates equivalent to those of parental strains. These strains did not differ from the parental strains in ultraviolet light sensitivity or the generation of petite colonies. Furthermore, these haploid deletion strains were capable of mating, the resultant diploid homozygous mutants were viable, capable of sporulation, and the spores displayed no reduction in viability. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 10 (1989), S. 333-348 
    ISSN: 0739-4462
    Keywords: serum proteins ; immunoelectrophoresis ; development ; insect ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The levels of an 81K storage protein in the waxmoth, Galleria mellonella, were monitored during the course of development using rocket immunoelectrophoresis. During the fifth and sixth larval stadia, 81K protein levels increased during feeding and growth but sharply declined at each larval molt. During the fifth and sixth stadia hemolymph levels of the 81K protein increased to about 1 and 2.5 mg/ml, respectively, with no discernible differences between levels in males and females. Neither the fat body nor the remainder of the carcass contained the 81K protein, indicating that the accumulation of this protein during the intermolt period was exclusively in the hemolymph and redistribution of the 81K protein into other tissues does not occur at the final two larval molts. During the seventh (final) larval stadium the absolute quantities of the 81K protein increased from 23 μg per insect to over 1,600 μg in females and to 300 μg in males. The hemolymph concentration of the 81K protein reached 28 mg/ml in females and 6 mg/ml in males with only low levels found in the remaining tissues. Shortly after pupal apolysis, marked by eyespot retraction, the fat body in both sexes rapidly and quantitatively sequestered the 81K protein from the hemolymph. The 81K protein in the hemolymph of both males and females rapidly dropped to nearly zero concentration by pupation. The 81K storage protein remained localized in the fat body cells after uptake occurred, even though the fat body cells disaggregate and reaggregate during metamorphosis. During pharate adult development the 81K storage protein disappeared from the fat body without entering the hemolymph. At adult eclosion 81K was virtually absent from the tissues of both males and females.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 15 (1990), S. 183-199 
    ISSN: 0739-4462
    Keywords: juvenile hormone ; metamorphosis ; oocyte development ; in vitro translation ; yolk proteins ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Vitellogenesis occurs during the late pharate adult stage in the Indianmeal moth, Plodia interpunctella. Repeated treatment of pharate adult females with doses of 20-hydroxyecdysone (20HE) from 10 to 250 ng per pupa suppressed oocyte growth and inhibited yolk protein accumulation in the oocytes. Treatment of the pharate adults with a biologically inactive ecdysteroid analogue, 22-isoecdysone, had no effect on egg maturation or yolk protein accumulation. The hormonal action of 20HE was not through the inhibition of the corpora allata or juvenile hormone levels, because treatment with a juvenile hormone analogue did not reverse the inhibition by 20HE treatment. Exposure of early vitellogenic ovaries to 20HE in organ cultures in vitro showed that 20HE had a direct effect on the ovarian synthesis of YP2. At 20HE concentrations below 10 nM, YP2 synthesis was minimal, at 10 nM 20HE YP2 synthesis was maximal, and at concentrations higher than 10 nM YP2 synthesis was suppressed to 35% of the maximal level. Synthesis of most other ovarian proteins remained constant with the changing 20HE concentrations. Ovarian RNA from treated females translated in a reticulocyte lysate demonstrated that the hormonal effect of 20HE on the ovarian tissues was on the specific accumulation of translatable YP2 transcript as well as transcripts for a few other polypeptides. This study shows that 20HE controls the rate of egg development during metamorphosis and that declining titers of 20HE regulate the expression of adult genes.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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