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  • 1
    Electronic Resource
    Electronic Resource
    Streptogramins-inactivating activity in three producer streptomycetes (1989)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 58 (1989), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The mechanism of self-resistance in three streptogramins-producing streptomycetes was analysed. The three organisms had ribosomes which were sensitive both to A- and B-components of the streptogramin complex. However, cell-free extracts of these producers showed streptogramins-inactivating activity which was independent on the addition of exogenous cofactors (S-adenosylmethionine, ATP or acetyl coenzyme A). The activity was retained by the extracts after dialysis and inactivated by boiling, indicating the presence of enzymatic activity. The inactivating activity was found throughout the growth cycle of the organisms indicating a constitutive nature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1989.tb03052.x
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  • 2
    Electronic Resource
    Electronic Resource
    MACROMOLECULAR SYNTHESIS DURING THE GERMINATION OF STREPTOMYCES SPORES IN A CHEMICALLY DEFINED MEDIUM (1980)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 7 (1980), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1980.tb01633.x
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  • 3
    Electronic Resource
    Electronic Resource
    Streptomyces antibioticus contains at least three oleandomycin-resistance determinants, one of which shows similarity with proteins of the ABC-transporter superfamily (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 8 (1993), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Three different DNA fragments of an oleandomycin producer, Streptomyces antibioticus, conferring oleandomycin resistance were cloned in plasmid pIJ702 and expressed in Streptomyces lividans and in Streptomyces albus. These oleandomycin resistance determinants were designated as oleA (pOR400), oleB (pOR501) and oleC (pOR800). oleA and oleC are closely linked in the chromosome as they were both obtained together in two cosmid clones that were isolated from a genomic library. Sequencing of the oleC resistance determinant revealed four complete open reading frames (ORFs) and the C-terminal end of a fifth. The functions of orf1 and orf2 are unknown since they did not show significant similarity with other sequences in the data bases. The orf3 gene product has similarity with some proteins involved in iron and vitamin B12 uptake in bacteria. The orf4 gene product had a hydrophilic profile and showed important similarity with proteins containing typical ATP-binding domains characteristic of the ABC-transporter superfamily and involved in membrane transport and, particularly, with several genes conferring resistance to various macrolide antibiotics and anticancer drugs. The last gene, orf5, is translationally coupled to orf4 and codes for a hydrophobic polypeptide containing several trans-membrane domains characteristic of integral membrane proteins. Subcloning and deletion experiments limited the resistance determinant to a 0.9kb Pst1-Sph1 fragment and only orf4 is included in this fragment. These results suggest that resistance to oleandomycin conferred by oleC (orf4) is probably due to an efflux transport system of the ABC-transporter superfamily.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1993.tb01601.x
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  • 4
    Electronic Resource
    Electronic Resource
    Two glycosyltransferases and a glycosidase are involved in oleandomycin modification during its biosynthesis by Streptomyces antibioticus (1998)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 28 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A 5.2 kb region from the oleandomycin gene cluster in Streptomyces antibioticus located between the oleandomycin polyketide synthase gene and sugar biosynthetic genes was cloned. Sequence analysis revealed the presence of three open reading frames (designated oleI, oleN2 and oleR). The oleI gene product resembled glycosyltransferases involved in macrolide inactivation including the oleD product, a previously described glycosyltransferase from S. antibioticus. The oleN2 gene product showed similarities with different aminotransferases involved in the biosynthesis of 6-deoxyhexoses. The oleR gene product was similar to several glucosidases from different origins. The oleI, oleR and oleD genes were expressed in Streptomyces lividans. OleI and OleD intracellular proteins were partially purified by affinity chromatography in an UDP-glucuronic acid agarose column and OleR was detected as a major band from the culture supernatant. OleI and OleD showed oleandomycin glycosylating activity but they differ in the pattern of substrate specificity: OleI being much more specific for oleandomycin. OleR showed glycosidase activity converting glycosylated oleandomycin into active oleandomycin. A model is proposed integrating these and previously reported results for intracellular inactivation, secretion and extracellular reactivation of oleandomycin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00880.x
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  • 5
    Electronic Resource
    Electronic Resource
    Interspecies complementation in Saccharopolyspora erythraea : elucidation of the function of oleP1, oleG1 and oleG2 from the oleandomycin biosynthetic gene cluster of Streptomyces antibioticus and generation of new erythromycin derivatives (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 34 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Two glycosyltransferase genes, oleG1 and oleG2, and a putative isomerase gene, oleP1, have previously been identified in the oleandomycin biosynthetic gene cluster of Streptomyces antibioticus. In order to identify which of these two glycosyltransferases encodes the desosaminyltransferase and which the oleandrosyltransferase, interspecies complementation has been carried out, using two mutant strains of Saccharopolyspora erythraea, one strain carrying an internal deletion in the eryCIII (desosaminyltransferase) gene and the other an internal deletion in the eryBV (mycarosyltransferase) gene. Expression of the oleG1 gene in the eryCIII deletion mutant restored the production of erythromycin A (although at a low level), demonstrating that oleG1 encodes the desosaminyltransferase required for the biosynthesis of oleandomycin and indicating that, as in erythromycin biosynthesis, the neutral sugar is transferred before the aminosugar onto the macrocyclic ring. Significantly, when an intact oleG2 gene (presumed to encode the oleandrosyltransferase) was expressed in the eryBV deletion mutant, antibiotic activity was also restored and, in addition to erythromycin A, new bioactive compounds were produced with a good yield. The neutral sugar residue present in these compounds was identified as l-rhamnose attached at position C-3 of an erythronolide B or a 6-deoxyerythronolide B lactone ring, thus indicating a relaxed specificity of the oleandrosyltransferase, OleG2, for both the activated sugar and the macrolactone substrate. The oleP1 gene located immediately upstream of oleG1 was likewise introduced into an eryCII deletion mutant of Sac. erythraea, and production of erythromycin A was again restored, demonstrating that the function of OleP1 is identical to that of EryCII in the biosynthesis of dTDP-d-desosamine, which we have previously proposed to be a dTDP-4-keto-6-deoxy-d-glucose 3,4-isomerase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01666.x
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  • 6
    Electronic Resource
    Electronic Resource
    Tailoring modification of deoxysugars during biosynthesis of the antitumour drug chromomycin A3 by Streptomyces griseus ssp. griseus (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 53 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Chromomycin A3 is a member of the aureolic acid group family of antitumour drugs. Three tailoring modification steps occur during its biosynthesis affecting the sugar moieties: two O-acetylations and one O-methylation. The 4-O-methylation in the 4-O-methyl-D-oliose moiety of the disaccharide chain is catalysed by the cmmMIII gene product. Inactivation of this gene generated a chromomycin-non-producing mutant that accumulated three unmethylated derivatives containing all sugars but differing in the acylation pattern. Two of these compounds were shown to be substrates of the methyltransferase as determined by their bioconversion into chromomycin A2 and A3 after feeding these compounds to a Streptomyces albus strain expressing the cmmMIII gene. The same single membrane-bound enzyme, encoded by the cmmA gene, is responsible for both acetyl transfer reactions, which convert a relatively inactive compound into the bioactive chromomycin A3. Insertional inactivation of this gene resulted in a mutant accumulating a dideacetylated chromomycin A3 derivative. This compound, lacking both acetyl groups, was converted in a two-step reaction via the 4E-monoacetylated intermediate into chromomycin A3 when fed to cultures of S. albus expressing the cmmA gene. This acetylation step would occur as the last step in chromomycin biosynthesis, being a very important event for self-protection of the producing organism. It would convert a molecule with low biological activity into an active one, in a reaction catalysed by an enzyme that is predicted to be located in the cell membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04166.x
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  • 7
    Electronic Resource
    Electronic Resource
    Insertional inactivation of mtrX and mtrY genes from the mithramycin gene cluster affects production and growth of the producer organism Streptomyces argillaceus (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 186 (2000), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Mithramycin is an antitumor aromatic polyketide synthesized by Streptomyces argillaceus. Two genes (mtrX and mtrY) of the mithramycin gene cluster were inactivated by gene replacement. Inactivation of mtrX, that encodes an ABC excission nuclease system for DNA repair, produced a mutant that was affected in the normal rate of growth. Expression of mtrX in Streptomyces albus in a multicopy plasmid vector conferred a low increase in resistance to mithramycin. Inactivation of mtrY, that encodes a protein of unknown function, produced a 50% decrease in mithramycin biosynthesis. When mtrY was expressed in the wild-type S. argillaceus in a multicopy plasmid, this caused about 47% increase in the levels of mithramycin production. It is proposed that mtrX and mtrY could code for a secondary defense mechanism and a mithramycin regulatory element, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2000.tb09082.x
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  • 8
    Electronic Resource
    Electronic Resource
    ABC transporters in antibiotic-producing actinomycetes (1998)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 158 (1998), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Many antibiotic-producing actinomycetes posses at least one ABC (ATP-binding cassette) transporter which forms part of the antibiotic biosynthetic pathway and in most cases confers resistance to the drug in an heterologous host. Three types of antibiotic ABC transporters have been so far described in producer organisms. In Type I two genes are involved, one encoding a hydrophilic ATP-binding protein with one nucleotide-binding domain and the other encoding a hydrophobic membrane protein. In Type II transporters only a gene encoding the hydrophilic ATP-binding protein with two nucleotide-binding domains is present and no gene encoding a hydrophobic membrane protein has been found. In Type III only one gene is involved which encodes both the hydrophilic and hydrophobic components. Possibly these ABC transporters are responsible for secretion of the antibiotics outside the cells. A comparative analysis of the ATP-binding components of the different antibiotic ABC transporters and analysis of the amino acid distances between the so-called Walker motifs suggests that the three types of transporters have probably evolved from a common ancestor containing a single nucleotide-binding domain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1998.tb12792.x
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  • 9
    Electronic Resource
    Electronic Resource
    Pathways of glucose catabolism during germination of Streptomyces spores (1984)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 22 (1984), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The participation of the different glucose-catabolic pathways during germination of Streptomyces antibioticus spores was studied. In dormant spores, glucose is catabolized through the pentose phosphate (PP) and the Embden-Meyerhof-Parnas (EMP) pathways, with an active tricarboxylic acid cycle. The relative participation of each catabolic pathway is regulated by germinative or non-germinative conditions. During spore germination, the pentose phosphate pathway continuously increased in its participation in the glucose catabolism and it was the major glucose-catabolic pathway in the exponential phase of growth. In addition, it showed the existence of an active tricarboxylic acid cycle in dormant spores, which was being drained for biosynthetic purposes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1984.tb00732.x
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  • 10
    Electronic Resource
    Electronic Resource
    Engineering specificity of starter unit selection by the erythromycin-producing polyketide synthase (2002)
    Oxford, UK : Blackwell Science Ltd.
    Molecular microbiology 43 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Chain initiation on many modular polyketide synthases is mediated by acyl transfer from the CoA ester of a dicarboxylic acid, followed by decarboxylation in situ by KSQ, a ketosynthase-like decarboxylase domain. Consistent with this, the acyltransferase (AT) domains of all KSQ-containing loading modules are shown here to contain a key arginine residue at their active site. Site-specific replacement of this arginine residue in the oleandomycin (ole) loading AT domain effectively abolished AT activity, consistent with its importance for catalysis. Substitution of the ole PKS loading module, or of the tylosin PKS loading module, for the erythromycin (ery) loading module gave polyketide products almost wholly either acetate derived or propionate derived, respectively, instead of the mixture found normally. An authentic extension module AT domain, rap AT2 from the rapamycin PKS, functioned appropriately when engineered in the place of the ole loading AT domain, and gave rise to substantial amounts of C13-methylerythromycins, as predicted. The role of direct acylation of the ketosynthase domain of ex-tension module 1 in chain initiation was confirmed by demonstrating that a mutant of the triketide synthase DEBS1-TE, in which the 4′-phosphopante-theine attachment site for starter acyl groups was specifically removed, produced triketide lactone pro-ducts in detectable amounts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02815.x
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