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  • 1
    Electronic Resource
    Electronic Resource
    Isolation and characterization of pteridines from heads of Drosophila melanogaster by a modified thin-layer chromatography procedure (1977)
    Springer
    Biochemical genetics 15 (1977), S. 307-319 
    Details
    ISSN: 1573-4927
    Keywords: pteridines ; Drosophila ; thin-layer chromatography ; eye pigments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract An improved thin-layer chromatography technique is described for the separation of fluorescent compounds found in extracts of heads of Drosophila melanogaster. Eighteen to twenty fluorescent spots are resolved, two of which are xanthurenic acid and 3-hydroxykynurenine, and the remaining spots are presumably pteridines. Of these, nine have been identified and quantitated directly on the chromatograms with a fluorometer. One of the spots present on the chromatogram apparently has not been described previous to this work. Characteristics of this substance, termed “quench spot,” are presented, several of which indicate that it may be a pteridine or pteridine derivative.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00484462
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanism of suppression in Drosophila. V. Localization of the purple mutant of Drosophila melanogaster in the pteridine biosynthetic pathway (1977)
    Springer
    Biochemical genetics 15 (1977), S. 321-332 
    Details
    ISSN: 1573-4927
    Keywords: pteridines ; Drosophila ; suppression ; eye color mutants ; GTP ; development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The suppressible eye color mutant purple (pr) of Drosophila melanogaster is known to be unable to synthesize a wild-type complement of pteridine eye pigments. This study measures the reduced levels of drosopterins, sepiapterin, and an unidentified presumed pteridine in pr and pr bw. Pteridine analyses in double mutants combining pr with one of three other eye color mutants sepia, Henna-recessive3, and prune2, suggest that the metabolic block in pr occurs prior to sepiapterin biosynthesis. Measurements of GTP and GTP cyclohydrolase in pr showed wild-type levels and indicate the metabolic block in pr to be at one of the steps converting dihydroneopterin triphosphate to sepiapterin. Quantitation of pteridines in suppressed purple [su(s) 2; pr and pr; su(pr) e3] shows restoration of pteridines to wild-type or nearly wild-type levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00484463
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Transport by reconstituted lactose carrier from parental and mutant strains ofEscherichia coli (1984)
    Springer
    The journal of membrane biology 79 (1984), S. 185-193 
    Details
    ISSN: 1432-1424
    Keywords: reconstitution ; lactose transport ; membrane potential ; pH gradient ; proteolytic enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The lactose transport carrier from parental (X71/F'W3747) and mutant cells (54/F'5441) was reconstituted into proteoliposomes. Transport by the counterflow assay showed slightly greater activity in proteoliposomes prepared from extracts of the mutant membranes compared with that for the parental cell. The mutant carrier showed a threefold lowerK m but similarV max compared to the parent. On the other hand proteoliposomes from the mutant showed a defect in protonmotive force-driven accumulation, compared with the parent. With a pH gradient (inside alkaline) plus a membrane potential (inside negative) the parental proteoliposomes accumulated lactose 25-fold over the medium concentration while the mutant proteoliposomes accumulated sixfold. In a series of experiments proteoliposomes were exposed to proteolytic enzymes. Chrymotrypsin treatment resulted in 30% inhibition of counterflow activity for the reconstituted carrier from both parent and mutant. Papain produced 84% inhibition of transport by the reconstituted parental carrier but only 41% of that of the mutant. Trypsin and carboxypeptidase Y treatment had no effect on counterflow activity of either parent or mutant. Exposure of purified lactose carrier in proteoliposomes to carboxypeptidase Y resulted in the release of alanine and valine, the two C-terminal amino acids predicted from the DNA sequence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01872122
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of different phospholipids on the reconstitution of two functions of the lactose carrier ofEscherichia coli (1985)
    Springer
    The journal of membrane biology 84 (1985), S. 259-267 
    Details
    ISSN: 1432-1424
    Keywords: proteoliposomes ; counterflow ; lactose carrier ; phospholipid requirement ; Escherichia coli ; reconstitution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The lactose carrier was extracted from membranes ofEscherichia coli and transport activity reconstituted in proteoliposomes containing different phospholipids. Two different assays f for carrier activity were utilized: counterflow and membrane potential-driven uptake. Proteoliposomes composed ofE. coli lipid or of 50% phosphatidylethanolamine−50% phosphatidylcholine showed very high transport activity with both assays. On the other hand, proteoliposomes containing asolectin, phosphatilcholine or 25% cholesterol/75% phosphatidylcholine showed good counterflow activity but poor membrane potentialdriven uptake. The discrepancy between the two types of transport activity in the latter group of three lipids is not due to leakiness to protons, size of proteoliposomes, or carrier protein content per proteoliposome. Apparently one function of the carrier molecule shows a broad tolerance for various phospholipids, while a second facet of the membrane protein activity requires very restricted lipid enviroment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871389
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    Paper (German National Licenses)
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