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Mode of action of the microbial metabolite GE23077, a novel potent and selective inhibitor of bacterial RNA polymerase

Authors :
Emiliana Corti
Enrico Selva
Edoardo Sarubbi
Anna Miele
Federica Monti
Source :
European Journal of Biochemistry. 271:3146-3154
Publication Year :
2004
Publisher :
Wiley, 2004.

Abstract

GE23077, a novel microbial metabolite recently isolated from Actinomadura sp. culture media, is a potent and selective inhibitor of bacterial RNA polymerase (RNAP). It inhibits Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) RNAPs with IC50 values (i.e. the concentration at which the enzyme activity is inhibited by 50%) in the 10−8 m range, whereas it is not active on E. coli DNA polymerase or on eukaryotic (wheat germ) RNAP II (IC50 values > 10−4 m in both cases). In spite of its potent activity on purified bacterial RNAPs, GE23077 shows a narrow spectrum of antimicrobial activity on Gram-positive and Gram-negative bacteria. To investigate the molecular basis of this behaviour, the effects of GE23077 on macromolecular biosynthesis were tested in E. coli cells permeabilized under different conditions. The addition of GE23077 to plasmolyzed cells resulted in an immediate and specific inhibition of intracellular RNA biosynthesis, in a dose–response manner, strongly suggesting that cell penetration is the main obstacle for effective antimicrobial activity of the antibiotic. Biochemical studies were also conducted with purified enzymes to obtain further insights into the mode of action of GE23077. Interestingly, the compound displays a behaviour similar to that of rifampicin, an antibiotic structurally unrelated to GE23077: both compounds act at the level of transcription initiation, but not on the σ subunit and not on the formation of the promoter DNA–RNAP complex. Tests on different rifampicin-resistant E. coli RNAPs did not show any cross-resistance between the two compounds, indicating distinct binding sites on the target enzyme. In conclusion, GE23077 is an interesting new molecule for future mechanistic studies on bacterial RNAP and for its potential in anti-infective drug discovery.

Details

ISSN :
14321033 and 00142956
Volume :
271
Database :
OpenAIRE
Journal :
European Journal of Biochemistry
Accession number :
edsair.doi...........e43e41a1cc25e93a09779c1ea7fa7532
Full Text :
https://doi.org/10.1111/j.1432-1033.2004.04244.x