Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The interaction of Rho and the antibiotic bicyclomycin was probed using in vitro transcription termination reactions, poly(C) binding assays, limited tryptic digestions, and the bicyclomycin inhibition kinetics of ATPase activity in the presence of poly(dC) and ribo(C)10. The approximate I50 value for the bicyclomycin inhibition of transcription termination at Rho-dependent sites within a modified trp operon template was 5 microM. At antibiotic concentrations near the I50 value, bicyclomycin inhibition of Rho-dependent transcripts was accompanied by the appearance of a new set of transcripts whose size was midway between the Rho-dependent transcripts and the readthrough transcripts. Bicyclomycin did not inhibit poly(C) binding to Rho. In the presence of poly(dC), bicyclomycin showed a reversible mixed inhibition of the ribo(C)10-stimulated ATPase activity. The extrapolated Ki for bicyclomycin was 2.8 microM without ribo(C)10 and increased to 26 microM in the presence of ribo(C)10. Correspondingly, the Km(app) for ribo(C)10 without bicyclomycin was 0.8 microM and with bicyclomycin was 5 microM at infinite inhibitor concentration. The data suggested that the antibiotic binds to Rho, influencing the secondary RNA binding (tracking) site on Rho and slows the tracking of Rho toward the bound RNA polymerase.
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PMID:The antibiotic bicyclomycin affects the secondary RNA binding site of Escherichia coli transcription termination factor Rho. 881 Mar 2

Molecular motors such as helicases/translocases are capable of translocating along the single-stranded nucleic acids and unwinding DNA or RNA duplex substrates using the energy derived from their ATPase activity. The bacterial transcription terminator, Rho, is a hexameric helicase and releases RNA from the transcription elongation complexes by an unknown mechanism. It has been proposed, but not directly demonstrated, that kinetic energy obtained from its molecular motor action (helicase/translocase activities) is instrumental in dissociating the transcription elongation complex. Here we report a hexameric Rho analogue (Rv1297, M. tb. Rho) from Mycobacterium tuberculosis having poor RNA-dependent ATP hydrolysis and inefficient DNA-RNA unwinding activities. However, compared to Escherichia coli Rho, it exhibited very robust and earlier transcription termination from the elongation complexes of E. coli RNA polymerase. Bicyclomycin, an inhibitor of ATPase as well as RNA release activities of E. coli Rho, inhibited the ATPase activity of M. tb. Rho with comparable efficiency but was not efficient in inhibiting its transcription termination function. Unlike E. coli Rho, M. tb. Rho was capable of releasing RNA in the presence of nonhydrolyzable analogues of ATP quite efficiently. Also, this termination function most likely does not require NusG, an RNA-release facilitator, as this Rho was incapable of binding to NusG either of M. tb. (Rv0639) or E. coli. These results strongly suggest that the ATPase activity of M. tb. Rho is uncoupled from its transcription termination function and this function may not be dependent on its helicase/translocase activity.
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PMID:A bacterial transcription terminator with inefficient molecular motor action but with a robust transcription termination function. 2002 69