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  • 1
    Electronic Resource
    Electronic Resource
    Molecular and genetic studies on the euchromatin-heterochromatin transition region of the X chromosome of Drosophila melanogaster (1984)
    Springer
    Chromosoma 89 (1984), S. 218-227 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A recombinant Charon 4 bacteriophage has been isolated on the basis of RNAs which are enriched in the head of the adult Drosophila melanogaster and hence are likely to be of neural origin. The cloned insert maps to the near vicinity of the uncoordinated locus in polytene chromosome band 19E8. This band is within the transition zone between the euchromatic and heterochromatic regions of the X chromosome, a region which has been well characterized cytogenetically. The insert contains both repetitious and low copy number sequences, some of which vary extensively in both frequency and restriction fragment size between different laboratory strains. One particular family of moderately repeated sequences occurs predominantly in divisions 19 and 20 of the X chromosome and perhaps the distally located X heterochromatin. The molecular landscape surrounding the initial entry point contains many repeated sequences and is thus unlike those observed in most published chromosomal walks. The possible significance of the presence of repeated sequence families in the distinct properties of this region are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00295003
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular analysis of thelethal(1)B214 region at the base of theX chromosome ofDrosophila melanogaster (1992)
    Springer
    Chromosoma 101 (1992), S. 456-466 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Approximately 50 kb of genomic DNA was isolated from polytene chromosome bands 19F1 and 2 ofDrosophila melanogaster. Bands 19F1 and 2 are in the immediate vicinity of the β-heterochromatin at the base of theX chromosome and encompass thelittle flylike andlethal(1)B214 complementation groups. The cloned DNA consists of an approximately 21 kb stretch of unique or low copy number sequence that is bounded by repetitive elements interspersed with further unique sequences. The presence of repeated sequences is characteristic of regions within and adjacent to β-heterochromatin. At least part of a tRNA gene cluster is present within the 50 kb of cloned DNA. The cloned region also produces at least 18 discrete size classes of developmentally regulated poly(A)+ RNA species. A 2 kb EcoRI fragment (E10), which lies in the 21 kb stretch of unique sequence, generates seven of these transcripts (of sizes 3.5, 3.35, 2.1, 2.0, 1.5, 1.2 and 1.0 kb) in wild-type flies. However, a small deletion of approximately 75 bp in E10 in alethal(1)B214 mutant allele is associated with alterations in the production or processing of all seven of these transcripts. These data identify E10 sequences as belonging to thelethal(1)B214 gene and suggest that the wild-typelethal(1)B214 gene encodes multiple transcripts. Furthermore, no transcripts of the same size and having the same developmental profile as those generated by the wild-type E10 fragment were identified by probes covering the remainder of the cloned region. This suggests that at least the larger transcripts hybridizing to E10 are partly transcribed from sequences located outside the cloned region, which indicates that thelethal(1)B214 gene extends for more than 20 kb and contains other transcriptionally active sequences within it.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582840
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of the EstP Protein in Drosophila melanogaster and Its Conservation in Drosophilids (1997)
    Springer
    Biochemical genetics 35 (1997), S. 251-271 
    Details
    ISSN: 1573-4927
    Keywords: EstP ; EST7 ; gene duplication ; gene regulation ; carboxylesterase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The β-esterase cluster of D. melanogaster comprises two tandemly duplicated genes. Est6 encodes the well-characterized 5′ gene, but the product of the second gene, denoted EstP, had not previously been identified. Here we show that the EstP gene encodes the carboxylesterase EST7. Expression of EstP using the Baculovirus system led to production of a carboxylesterase biochemically indistinguishable from EST7. Furthermore, a naturally occurring EstP variant produces greatly reduced amounts of EstP mRNA and no detectable EST7 protein. Finally, introduction of a wild-type copy of EstP by germline transformation into the variant strain confers the wild-type EST7 phenotype. We show that EST7 differs from EST6 in its substrate and inhibitor specificities and tissue distribution. Germline transformation experiments show that EstP expression is controlled by sequences located between 192 bp 5′ and 609 bp 3′ of the EstP coding region. Data comparisons with other drosophilid esterases suggest that the site of expression, and hence the function, of EST7 has been conserved across lineages in both the subgenera Drosophila and Sophophora.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021897016276
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of the residue adjacent to the reactive serine on the substrate interactions ofDrosophila esterase 6 (1993)
    Springer
    Biochemical genetics 31 (1993), S. 259-278 
    Details
    ISSN: 1573-4927
    Keywords: serine esterase ; substrate interactions ; Drosophila ; acetylcholine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Esterase 6 fromDrosophila melanogaster is a carboxylesterase that belongs to the serine esterase multigene family. It has a basic histidine (His) at residue 187, adjacent to the reactive serine (Ser) at residue 188, whereas most other characterized members of the family have an acidic glutamate (Glu) in the equivalent position. We have used site-directedin vitro mutagenesis to replace the His codon of the esterase 6 gene with either Gln or Glu codons. The enzymes encoded by these active-site mutants and a wild-type control have been expressed, purified, and characterized. Substitution of Gln for His at position 187 has little effect on the biochemical properties of esterase 6, but the presence of Glu at this position is associated with three major differences. First, the pH optimum is increased from 7 to 9. Second, the mutant enzyme shows decreased activity for β-naphthyl esters andp-nitrophenyl acetate but has gained the ability to hydrolyze acetylthiocholine. Finally, the Gibb's free energy of activation for the enzyme is increased. These results suggest that residue 187 interacts directly with the substrate alkyl group and that this interaction is fully realized in the transition state. We further propose that the presence of His rather than Glu at position 187 in esterase 6 contributes significantly to its functional divergence from the cholinesterases and that this divergence is due to different interactions between residue 187 and the substrate alkyl group.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00553170
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of the residue adjacent to the reactive serine on the substrate interactions ofDrosophila esterase 6 (1993)
    Springer
    Biochemical genetics 31 (1993), S. 259-278 
    Details
    ISSN: 1573-4927
    Keywords: serine esterase ; substrate interactions ; Drosophila ; acetylcholine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Esterase 6 fromDrosophila melanogaster is a carboxylesterase that belongs to the serine esterase multigene family. It has a basic histidine (His) at residue 187, adjacent to the reactive serine (Ser) at residue 188, whereas most other characterized members of the family have an acidic glutamate (Glu) in the equivalent position. We have used site-directedin vitro mutagenesis to replace the His codon of the esterase 6 gene with either Gln or Glu codons. The enzymes encoded by these active-site mutants and a wild-type control have been expressed, purified, and characterized. Substitution of Gln for His at position 187 has little effect on the biochemical properties of esterase 6, but the presence of Glu at this position is associated with three major differences. First, the pH optimum is increased from 7 to 9. Second, the mutant enzyme shows decreased activity for β-naphthyl esters andp-nitrophenyl acetate but has gained the ability to hydrolyze acetylthiocholine. Finally, the Gibb’s free energy of activation for the enzyme is increased. These results suggest that residue 187 interacts directly with the substrate alkyl group and that this interaction is fully realized in the transition state. We further propose that the presence of His rather than Glu at position 187 in esterase 6 contributes significantly to its functional divergence from the cholinesterases and that this divergence is due to different interactions between residue 187 and the substrate alkyl group.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02401822
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  • 6
    Electronic Resource
    Electronic Resource
    Biochemical and physiological studies of soluble esterases fromDrosophila melanogaster (1991)
    Springer
    Biochemical genetics 29 (1991), S. 365-388 
    Details
    ISSN: 1573-4927
    Keywords: Drosophila melanogaster ; esterases ; biochemical properties ; expression pattern
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Twenty-two soluble esterases have been identified inD. melanogaster by combining the techniques of native polyacrylamide gel electrophoresis and isoelectric focusing. The sensitivity of each isozyme to three types of inhibitors (organophosphates, eserine sulfate, and sulfydryl reagents) identified 10 as carboxylesterases, 6 as cholinesterases, and 3 as acetylesterases. Three isozymes could not be classified and no arylesterases were identified. The carboxyl- and cholinesterases could each be further divided into two subclasses on the basis of inhibition by organophosphates and sulfhydryl reagents, respectively. Cholineand acetylesterases have characteristic substrate preferences but both subclasses of carboxylesterases are heterogeneous in substrate utilization. Subclass 2 carboxylesterases exhibit diverse temporal expression patterns, with subclass 1 carboxylesterases generally found in larvae and subclass 1 cholinesterases and acetylesterases more characteristic of pupae and adults. Tissues showing the greatest number of isozymes are larval body wall (eight) and digestive tract (six in larvae, six in adults). Carboxylesterases are distributed across a wide range of tissues, but subclass 1 cholinesterases are generally associated with neural or neurosecretory tissues and subclass 2 cholinesterases with digestive tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00554144
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  • 7
    Electronic Resource
    Electronic Resource
    Mutational analysis ofN-linked glycosylation of esterase 6 inDrosophila melanogaster (1996)
    Springer
    Biochemical genetics 34 (1996), S. 201-218 
    Details
    ISSN: 1573-4927
    Keywords: Drosophila ; esterase 6 ; glycosylation ; mutagenesis ; reproduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The primary sequence of the esterase 6 (EST6) enzyme ofDrosophila melanogaster contains four potential N-linked glycosylation sites, at residues 21, 399, 435, and 485. Here we determine the extent to which EST6 is glycosylated and how the glycosylation affects the biochemistry and physiology of the enzyme. We have abolished each of the four potential glycosylation sites by replacing the required Asn residues with Gln byin vitro mutagenesis. Five mutant genes were made, four containing mutations of each site individually and the fifth site containing all four mutations. Germline transformation was used to introduce the mutant genes into a strain ofD. melanogaster null for EST6. Electrophoretic and Western blot comparisons of the mutant strains and wild-type controls showed that each of the four potential N-linked glycosylation sites in the wild-type protein is glycosylated. However, the fourth site is not utilized on all EST6 molecules, resulting in two molecular forms of the enzyme. Digestion with specific endoglycosidases showed that the glycan attached at the second site is of the high-mannose type, while the other three sites carry more complex oligosaccharides. The thermostability of the enzyme is not affected by abolition of the first, third, or fourth glycosylation sites but is reduced by abolition of the second site. Anomalously, abolition of all four sites together does not reduce thermostability. Quantitative comparisons of EST6 activities showed that abolition of glycosylation does not affect the secretion of the enzyme into the male sperm ejaculatory duct, its transfer to the female vagina during mating, or its subsequent translocation into her hemolymph. However, the activity of the mutant enzymes does not persist in the female's hemolymph for as long as wild-type esterase 6. The latter effect may compromise the role of the transferred enzyme in stimulating egg-laying and delaying receptivity to remating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00553667
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  • 8
    Electronic Resource
    Electronic Resource
    Mutational analysis ofN-linked glycosylation of esterase 6 inDrosophila melanogaster (1996)
    Springer
    Biochemical genetics 34 (1996), S. 201-218 
    Details
    ISSN: 1573-4927
    Keywords: Drosophila ; esterase 6 ; glycosylation ; mutagenesis ; reproduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The primary sequence of the esterase 6 (EST6) enzyme ofDrosophila melanogaster contains four potential N-linked glycosylation sites, at residues 21, 399, 435, and 485. Here we determine the extent to which EST6 is glycosylated and how the glycosylation affects the biochemistry and physiology of the enzyme. We have abolished each of the four potential glycosylation sites by replacing the required Asn residues with Gln byin vitro mutagenesis. Five mutant genes were made, four containing mutations of each site individually and the fifth site containing all four mutations. Germline transformation was used to introduce the mutant genes into a strain ofD. melanogaster null for EST6. Electrophoretic and Western blot comparisons of the mutant strains and wild-type controls showed that each of the four potential N-linked glycosylation sites in the wild-type protein is glycosylated. However, the fourth site is not utilized on all EST6 molecules, resulting in two molecular forms of the enzyme. Digestion with specific endoglycosidases showed that the glycan attached at the second site is of the high-mannose type, while the other three sites carry more complex oligosaccharides. The thermostability of the enzyme is not affected by abolition of the first, third, or fourth glycosylation sites but is reduced by abolition of the second site. Anomalously, abolition of all four sites together does not reduce thermostability. Quantitative comparisons of EST6 activities showed that abolition of glycosylation does not affect the secretion of the enzyme into the male sperm ejaculatory duct, its transfer to the female vagina during mating, or its subsequent translocation into her hemolymph. However, the activity of the mutant enzymes does not persist in the female's hemolymph for as long as wild-type esterase 6. The latter effect may compromise the role of the transferred enzyme in stimulating egg-laying and delaying receptivity to remating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02407020
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular studies on interspersed repetitive and unique sequences in the region of the complementation group uncoordinated on the X chromosome of Drosophila melanogaster (1988)
    Springer
    Molecular genetics and genomics 213 (1988), S. 63-71 
    Details
    ISSN: 1617-4623
    Keywords: Drosophila ; Uncoordinated gene ; Repetitive DNA ; Type 1 insertion sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The technique of chromosome walking was used to isolate approximately 60 kb of DNA from the region containing the complementation group uncoordinated of Drosophila melanogaster, located in that part of the X chromosome which spans the euchromatin-heterochromatin junction. The cloned DNA can be divided into two distinct regions. The first contains sequences that are low copy number or unique and are largely conserved between strains. The second region is characterized by units repeated in tandem arrays and is polymorphic within, and between, strains. Each repetitive unit is separated by a member of an abundant sequence family, part of which is homologous to the ribosomal type 1 insertion sequence of D. melanogaster. The molecular organization of the cloned DNA was compared with that of sequences isolated from regions of intercalary heterochromatin and also with genes which have been characterized from more conventional euchromatic regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00333399
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  • 10
    Electronic Resource
    Electronic Resource
    Associations of esterase 6 allozyme and activity variation with reproductive fitness inDrosophila melanogaster (1994)
    Springer
    Genetica 94 (1994), S. 43-56 
    Details
    ISSN: 1573-6857
    Keywords: Drosophila ; esterase 6 ; reproduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Previous studies have shown that the esterase 6 (EST6) enzyme ofD. melanogaster is mainly produced in the sperm ejaculatory duct of the adult male and comparisons of wild-type males with laboratory null mutants have suggested that the enzyme plays a role in reproductive fitness. In this study we have compared 18 field-derived lines each isoallelic forEst6 for differences in five components of male reproductive fitness. No consistent fitness differences were found among lines differing in respect of the two major allozyme classes EST6-F and EST6-S, despite other evidence that these two classes are not selectively equivalent in the field. However, differences in reproductive fitness were found among lines differing in the minor mobility variants that segregate within EST6-F and EST6-S. A failure to distinguish among these minor forms may explain the discrepancies in previous studies on the effects of the major EST6 allozymes on reproductive fitness. The most significant associations we have found between EST6 and reproductive fitness were due to variation in EST6 activity levels. Male EST6 activity levels were found to be positively correlated with their time to first mating, negatively correlated with the numbers of eggs laid and progeny produced by their mates, and negatively correlated with the frequency with which their mates remate. We conclude that some EST6 variants differ in components of male reproductive fitness operative in laboratory cultures. However, the evidence for fitness differences is stronger for variants affecting the amount, rather than the structure of the enzyme, and the direction of the differences varies between some of the fitness components tested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01429219
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