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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of secondary, integration sites for IS117 in Streptomyces lividans and their role in the generation of chromosomal deletions (1993)
    Springer
    Molecular genetics and genomics 239 (1993), S. 90-96 
    Details
    ISSN: 1617-4623
    Keywords: Transposable element ; Site-specific integration ; DNA rearrangement ; Deletion formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract IS117, the 2.6 kb mini-circle of Streptomyces coelicolor A3(2), is a transposable element previously shown to be integrated into two distant sites in the chromosome. When introduced into S. lividans, IS117 integrates into one preferred chromosomal site, but when this site was artificially deleted, IS117 integrated into many secondary sites. Nucleotide sequence analysis of several secondary integration sites revealed varying degrees of similarity with the preferred site, but no consensus sequence. Nevertheless, sites more similar to the preferred site tended to be occupied more often than those that are less similar. Insertion of IS117 into secondary sites in the chromosome of S. lividans sometimes mediated chromosomal rearrangements. It was shown that some strains containing IS117 integrated into secondary sites had suffered deletions of chromosomal DNA. Deletions were adjacent to the inserted element and were at least several kilobases long. The proposed model implicates homologous recombination between IS117 copies integrated into two different secondary sites in the same chromosome as a cause of the deletions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00281606
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  • 2
    Electronic Resource
    Electronic Resource
    Organisation and functions of the actV A region of the actinorhodin biosynthetic gene cluster of Streptomyces coelicolor (1991)
    Springer
    Molecular genetics and genomics 230 (1991), S. 401-412 
    Details
    ISSN: 1617-4623
    Keywords: Antibiotic biosynthesis ; Antibiotic resistance ; Hydroxylases ; Streptomyces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Sequence analysis of the actVA region of the actinorhodin biosynthetic gene cluster of Streptomyces coelicolor revealed a succession of six open reading frames (ORFs), all running in the same direction and extending over 5.32 kb. The protein product of actVA-ORF1 strongly resembles that of another gene, elsewhere in the act cluster (actII-ORF2), which codes for a trans-membrane protein previously implicated in actinorhodin export from the mycelium. This suggests that the two gene products may co-operate in actinorhodin export, perhaps being sufficient for self-protection of the organism against suicide. At least four of the other five ORFs are implicated in the control of the C-6 and C-8 ring-hydroxylation reactions, lacking in actVA mutants, that occur at middle to late stages in the actinorhodin biosynthetic pathway. This conclusion was reached by genetic mapping of actVA mutants to actVA-ORF3 and-ORF5 (and perhaps -ORF4), and by the finding of strong resemblances between the protein products of actVA-ORF2 and -ORF6 and the products of genes of the oxytetracycline or tetracenomycin gene clusters that have been implicated in ring-hydroxylation reactions in the biosynthesis of these other aromatic polyketide antibiotics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00280297
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  • 3
    Electronic Resource
    Electronic Resource
    Characterisation of actI-homologous DNA encoding polyketide synthase genes from the monensin producer Streptomyces cinnamonensis (1992)
    Springer
    Molecular genetics and genomics 234 (1992), S. 254-264 
    Details
    ISSN: 1617-4623
    Keywords: Streptomyces cinnamonensis ; Polyether ; Antibiotic biosynthesis ; Polyketide synthase ; Actinorhodin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cloned DNA encoding polyketide synthase (PKS) genes from one Streptomyces species was previously shown to serve as a useful hybridisation probe for the isolation of other PKS gene clusters from the same or different species. In this work, the actI and actIII genes, encoding components of the actinorhodin PKS of Streptomyces coelicolor, were used to identify and clone a region of homologous DNA from the monensin-producing organism S. cinnamonensis. A 4799 by fragment containing the S. cinnamonensis act-homologous DNA was sequenced. Five open reading frames (ORFs 1–5) were identified on one strand of this DNA. The five ORFs show high sequence similarities to ORFs that were previously identified in the granaticin, actinorhodin, tetracenomycin and whiE PKS gene clusters. This allowed the assignment of the following putative functions to these five ORFS : a heterodimeric β-ketoacyl synthase (ORF1 and ORF2), an acyl carrier protein (ORF3), a β-ketoacyl reductase (ORF5), and a bifunctional cyclase/dehydrase (ORF4). The ORFs are encoded in the order ORFl-ORF2-ORF3-ORF5-ORF4, and ORFs-1 and -2 show evidence for translational coupling. This act-homologous region therefore appears to encode a PKS gene cluster. A gene disruption experiment using the vector pGM 160, and other evidence, suggests that this cluster is not essential for monensin biosynthesis but rather is involved in the biosynthesis of a cryptic aromatic polyketide in S. cinnamonensis. An efficient plasmid transformation system for S. cinnamonensis has been established, using the multicopy plasmids pWOR120 and pWOR125.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00283846
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  • 4
    Electronic Resource
    Electronic Resource
    Transposition of IS117 (the Streptomyces coelicolor A3(2) mini-circle) to and from a cloned target site and into secondary chromosomal sites (1990)
    Springer
    Molecular genetics and genomics 224 (1990), S. 65-71 
    Details
    ISSN: 1617-4623
    Keywords: Streptomyces ; Transposable element ; ϕC31 phage ; Gene replacement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary IS117, previously known as the 2.6 kb minicircle, is a transposable element found in Streptomyces coelicolor A3(2). It integrates predominantly into one preferred site when introduced into the closely related Streptomyces lividans 66, which lacks IS117. This preferred integration site was deleted from the S. lividans chromosome by replacement with an erythromycin resistance gene delivered by a ϕC31 phage vector. When IS117 was introduced into the resulting strain it integrated into many other sites, with some indication of site preference. By cloning a 200 by fragment centred on the preferred integration site onto a low copy number, self-transmissible Streptomyces plasmid derived from SCP2* it was shown that this sequence is sufficient to define the preferred site: IS117 integrates efficiently into this sequence from its preferred site in the host chromosome and at a lower frequency from the plasmid into the preferred site on the S. lividans chromosome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00259452
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  • 5
    Electronic Resource
    Electronic Resource
    Transcriptional organization and regulation of an antibiotic export complex in the producing Streptomyces culture (1991)
    Springer
    Molecular genetics and genomics 228 (1991), S. 372-380 
    Details
    ISSN: 1617-4623
    Keywords: Streptomyces ; Antibiotic export ; Repressor ; S1 mapping ; Divergent promoters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Three open reading frames (ORFs) in the actII region of the actinorhodin biosynthetic gene cluster of Streptomyces coelicolor A3(2), which are involved in the export of the antibiotic are carried on two divergent transcripts. A monocistronic transcript carries actII-ORF1, encoding a putative repressor protein, and a bicistronic transcript codes for actII-ORF2 and -ORF3, whose products have been postulated to form an antibiotic export complex. The actll-ORF1 and actll-ORF2/3 transcripts each have a single promoter and the promoters for the two transcripts overlap. Both promoters are most active in cultures that have developed to the stage of actinorhodin production. The promoters resemble consensus promoters of the vegetative class in Escherichia coli and Streptomyces. We also demonstrate that these promoters are expressed in E. coli and use this finding to reveal a regulatory role for the repressor, using the xy/E reporter gene on promoter-probe shuttle vectors and regulated expression of the actII-ORF1 gene under control of Plac. The actII-ORF2/3 promoter is strongly repressed by the ORF1 product and the ORF1 product also represses its own promoter. The finding that the operator/promoter arrangement, and regulatory interconnection, of an antibiotic export/repressor gene pair in Streptomyces strikingly resemble those for tetracycline resistance in bacteria of clinical importance supports the hypothesis of an evolutionary origin of such genes in an ancestral actinomycete.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260629
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