Echinomycin, daunomycin, ethidium bromide, nogalamycin, chromomycin, mithramycin, and olivomycin inhibit RNA synthesis by RNA polymerase by interacting with the DNA template. Chromomycin and olivomycin form complexes with DNA, preferably in the helical form, but not with RNA. These complexes require guanine in DNA and the addition of a stoichiometric amount of bivalent cation. None of the other antibiotics requires the presence of any single base in the template for its action.

Base Specificity in the Interaction of Polynucleotides with Antibiotic Drugs

The application of molecular cloning to antibiotic-producing microorganisms should lead to enhanced antibiotic productivity and to the biosynthesis of novel antibiotics by in vitro interspecific recombination. To allow such approaches, the genes for antibiotic synthesis must be isolated, analysed and perhaps modified. Certain Streptomyces species produce nearly two-thirds of the known natural antibiotics; the recent development of cloning systems in the genus makes it possible to isolate and analyse Streptomyces genes. However, antibiotics are metabolites which require sets of several enzymes for their synthesis and attempts to isolate the corresponding genes have so far yielded clones carrying either individual genes of the set, or only incomplete gene sets. We describe here the isolation of a large continuous segment of Streptomyces coelicolor DNA which apparently carries the complete genetic information required for synthesis of an antibiotic, actinorhodin , from simple primary metabolites. Not only can the cloned DNA 'complement' all available classes of actinorhodin non-producing mutants of S. coelicolor but, on introduction into a different host, Streptomyces parvulus , it directs the synthesis of the antibiotic. The tendency for the genes for antibiotic synthesis to be clustered together on the chromosomes of Streptomyces species and the availability of plasmid vectors which can carry stable inserts of DNA larger than 30 kilobase pairs (kb) and which can be introduced efficiently into Streptomyces protoplasts, suggest that the experiments described have general significance for this area of biotechnology.

Molecular cloning of the whole biosynthetic pathway of a Streptomyces antibiotic and its expression in a heterologous host

Biosynthesis of polyketides by trans-AT polyketide synthases

The recent development of molecular cloning systems in Streptomyces has made possible the isolation of biosynthetic genes for some of the many antibiotics produced by members of this important genus of bacteria. Such clones can now be used to test the idea that novel antibiotics could arise through the transfer of biosynthetic genes between streptomycetes producing different antibiotics. The likelihood of a 'hybrid' compound being produced must depend on the substrate specificities of the biosynthetic enzymes, about which little is known. In attempts to demonstrate hybrid antibiotic production, we therefore began with strains producing different members of the same chemical class of compounds in order to maximize the chance of success. Here we report the production of novel compounds by gene transfer between strains producing the isochromanequinone antibiotics actinorhodin, granaticin and medermycin. These experiments were made possible by the recent cloning of the whole set of genes for the biosynthetic pathway of actinorhodin from Streptomyces coelicolor A3(2) (ref. 8). We believe that this represents the first report of the production of hybrid antibiotics by genetic engineering.

Production of 'hybrid' antibiotics by genetic engineering.

N-Methylation is one of the simplest chemical modifications often occurring in peptides and proteins of prokaryotes and higher eukaryotes. Over years of evolution, nature has employed N-methylation of peptides as an ingenious technique to modulate biological function, often as a mode of survival through the production of antibiotics. This small structural change can not only mobilize large protein complexes (as in the histone methylation), but also inhibits the action of enzymes by selective recognition of protein-protein interaction surfaces. In recent years through the advancement in synthetic approaches, the potential of N-methylation has begun to be revealed, not only in modulating biological activity and selectivity as well as pharmacokinetic properties of peptides, but also in delivering novel drugs. Herein, we summarize the current knowledge of the versatility of N-methylation in modulating biological, structural, and pharmacokinetic properties of peptides.

N-methylation of peptides and proteins: an important element for modulating biological functions.

Aus Kulturfiltrat und Mycel eines Streptomyces viridochromogenes oder Streptomyces olivochromogenes nahestehenden Streptomyceten wurde neben Actidion eine neutrale, farblose, kristalline Verbindung C30H48O9, das Nonactin, isoliert, die chemisch wenig reaktiv ist und gegenuber den untersuchten Mikroorganismen unwirksam oder nur schwach wirksam war.

Stoffwechselprodukte von Actinomyceten. 3. Mitteilung. Nonactin

Aus den Kulturbruhen von Streptomyces echinatus n. sp. wurde ein neues lipophiles, neutrales Antibioticum – das Echinomycin, C29H37O7N7S – isoliert und durch analytische Daten, UV.- und IR.- Absorptionsspektrum, sowie biologische Wirksamkeit charakterisiert.

Stoffwechselprodukte von Actinomyceten. 7. Mitteilung. Echinomycin

Aus dem Kulturfiltrat eines Streptomyceten-Stammes, der vorlaufig bei Streptomyces olivaceus (Waksman) Waksman & Henrici eingeordnet wurde, liess sich ein kristalliner, antibiotisch wirksamer Farbstoff mit lackmusahnlichen Eigenschaften—das Granaticin—isolieren. Wie aus dem auf rontgenographischem Wege bestimmten Molekulargewicht, den analytischen Daten und Absorptionsspektren des Farbstoffes und seines Tetra-O-acetyl-Derivates folgt, handelt es sich vermutlich um eine tricyclische Tetrahydroxy-chinon-dicarbonsaure C22H20O10.

Stoffwechselprodukte von Actinomyceten. 9. Mitteilung. Granaticin

Aus den Kulturbruhen eines Stammes von Streptomyces violaceoniger (WAKSMANet CURTIS) WAKSMANet HENRICI wurden zwei neutrale, farblose Antibiotica isoliert: Lankamycin, C36H62O14, und Lankacidin, C46H66O16N2. Das Lankamycin gehort seinem chemischen und biologischen Verhalten nach zu den Makroliden.

Stoffwechselprodukte von Actinomyceten. 21. Mitteilung. Lankamycin und Lankacidin

Das gelbe, lipophile Antibioticum Holomycin, C7,H6;O2,N2,S2, welches aus den Kulturfiltraten des Actinomyceten-Stammes ETH. 17474 isoliert wurde, besitzt die Konstitution IV eines Des-N-methyl-thiolutins.

L. Neipp

Papers

Stoffwechselprodukte von Actinomyceten. 3. Mitteilung. Nonactin

Stoffwechselprodukte von Actinomyceten. 7. Mitteilung. Echinomycin

Stoffwechselprodukte von Actinomyceten. 9. Mitteilung. Granaticin

Stoffwechselprodukte von Actinomyceten. 21. Mitteilung. Lankamycin und Lankacidin

Stoffwechselprodukte von Actinomyceten 17. MitteilungHolomycin