Affiliation:
1. Biosearch Italia s.p.a., 21040 Gerenzano (VA),1
2. Dipartimento di Biologia e Patologia Cellulare e Molecolare, Centro di Endocrinologia ed Oncologia Sperimentale of the C.N.R., 80131 Naples,2 and
3. Istituto Internazionale di Genetica e Biofisica of the C.N.R., 80125 Naples,3 Italy
Abstract
ABSTRACT
Bicyclomycin is a commercially important antibiotic that has been shown to be effective against many gram-negative bacteria. Genetic and biochemical evidence indicates that the antibiotic interferes with RNA metabolism in
Escherichia coli
by inhibiting the activity of transcription termination factor Rho. However, the precise mechanism of inhibition is not completely known. In this study we have used in vitro transcription assays to analyze the effects of bicyclomycin on the termination step of transcription. The Rho-dependent transcription termination region located within the
hisG
cistron of
Salmonella typhimurium
has been used as an experimental system. The possible interference of the antibiotic with the various functions of factor Rho, such as RNA binding at the primary site, ATP binding, and hexamer formation, has been investigated by RNA gel mobility shift, photochemical cross-linking, and gel filtration experiments. The results of these studies demonstrate that bicyclomycin does not interfere with the binding of Rho to the loading site on nascent RNA. Binding of the factor to ATP is not impeded, on the contrary, the antibiotic appears to decrease the apparent equilibrium dissociation constant for ATP in photochemical cross-linking experiments. The available evidence suggests that this decrease might be due to an interference with the correct positioning of ATP within the nucleotide-binding pocket leading b an inherent block of ATP hydrolysis. Possibly, as a consequence of this interference, the antibiotic also prevents ATP-dependent stabilization of Rho hexamers.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Pharmacology (medical),Pharmacology
Cited by
13 articles.
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