Rifamycin-mode of action, resistance, and biosynthesis.

Studies of the binding of Escherichia coli RNA polymerase to DNA. I. The role of sigma subunit in site selection.

The RNA polymerase σ factor is required for the initiation of RNA synthesis. After initiation σ is released from the polymerase-factor complex and from the DNA template, and may then be re-used by another polymerase molecule to initiate a new RNA chain.

Cyclic re-use of the RNA polymerase sigma factor.

Candida lipolytica synthetisiert das Antibioticum Tryptanthrin aus 1 Mol Tryptophan und 1 Mol Anthranilsaure. Bei Verfutterung von Tryptophan und substituierter Anthranilsaure, bzw. substituiertem Tryptophan und Anthranilsaure, konnten die zu erwartenden Tryptanthrinderivate isoliert und identifiziert werden. Die Enzyme der Tryptanthrinbiosynthese wiesen in bezug auf diese Substrate, mit Ausnahme von Bromtryptophan, keine Spezifitat auf. Parallel zu diesen Versuchen wurden durch chemische Synthese substituierte Tryptanthrine hergestellt. Die Dierivate wurden auf ihre antibiotische Wirksamkeit gepruft; als besonders wirksam erwiesen sich die halogenierten Verbindungen.

Stoffwechselprodukte von Mikroorganismen

Interaction of rifamycin with bacterial RNA polymerase.

Fig. 1. Effect of rifamycins on RNA polymerase reactions of E. coli and Ehrlich carcinoma cells. The reaction mixture for the assay of E. coli RNA polymerase contained (0.3 ml) Tris-HCl, pH 8.0, 15 //moles; /?-mercaptoethanol, 3.6 //moles; MgCl2, 1.2 //moles; MnCl2, 0.3 //moles; ATP, GTP and UTP, 0.1 //mole each; 3H-CTP, 0.05 //moles (3,000 cpm/m/zmole); calf thymus DNA, 30 jug, enzyme, 20jug. Incubation was at 37°C for 10 minutes. The mixture for the assay of Ehrlich cell RNA polymerase contained (0.3 ml) Tris-HCl, pH 7.8, 15 //moles; j9-mercaptoethanol, 3 //moles; MgCl2, 2.4 //moles; MnCl2, 0.6 //mole; ATP, GTP and UTP, 0.1 //mole each; ^H-CTP, 0.012 //mole (30,000 cpm/m/zmole) ; calf thymus DNA, 25 jug; enzyme, 0.34 mg. Incubation was at 37°C for 20 minutes. /Op l/OO whether rifamycins have the same mode of action on DNA-dependent RNA synthesis of E. coli because of their structural resem blance4^ In this communication, we report the mode of action of rifamycin B and rifamycin SV on DNA-dependent RNA polymerase reac tions of both E. coli and Ehrlich ascites carcinoma cells. DNA-dependent RNA polymerase from E. coli B was prepared by the method of Chamberlin and Berg5) and that from Ehrlich ascites cells was extracted as reported pre viously^. The procedure for the assay of RNA polymerase was the same as described in a previous paper2). Rif mycin B and rifamycin SV were kindly given by Dr. P. Sensi, Research La boratories, Lepetit, S.p.A., Milan, Italy. Fig. 1 shows the effect of rifamycin B and rifamycin SV on DNA-dependent RNA poly merase reactions of E. coli and of Ehrlich ascites carcinoma cells. The results indicate that the incorporation of 3H-CMP into acid insoluble fraction by RNA polymerase of E. coli was markedly inhibited by both anti biotics at a concentration as low as 0.1 jum. However, the 3H-CMP incorporation by RNA polymerase of Ehrlich ascites carci

Hisaji Yamazaki

Papers

Inhibition of dna-dependent rna synthesis by rifamycins

Inhibition of DNA-dependent RNA polymerase reaction of Escherichia coll by an antimicrobial antibiotic, streptovaricin

Immunosuppression induced with cell-free fluid of Ehrlich carcinoma ascites and its fractions.

Inhibition of initiation of DNA-dependent RNA synthesis by an antibiotic B44p.

Streptovaricin- and rifampigin-resistange of rna polymerase in a resistant clone of escherichia coli b