Novobiocin inhibits the self-splicing of the primary transcripts of T4 phage thymidylate synthase gene
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Effects of the antibiotic novobiocin on the self-splicing of primary transcripts of the phage T4 thymidylate synthase gene (td) have been investigated. Novobiocin at 10 mM concentration inhibited the splicing by about 5% but at 40 mM concentration the splicing rate was inhibited by about 50%. The novobiocin inhibition of the self-splicing reaction was not reversed even at a high concentration (200 μM) of guanosine. However, increasing the Mg2+ ion concentrations up to 20 mM almost fully restored the splicing activity to the normal splicing level. The double reciprocal plot analysis demonstrated that novobiocin acts as a mixed noncompetitive inhibitor for the td intron RNA with a K i of 90 mM. The splicing inhibition by novobiocin was strongly dependent on Mg2+ ion concentration, indicating electrostatic interactions with the td intron RNA. It is likely that the antibiotic novobiocin may interfere with the catalytic actions of Mg2+ ion in the splicing reaction of the td intron RNA.
KeywordsPhage T4 td intron RNA Novobiocin Self-splicing Noncompetitive inhibition
We sincerely thank Dr. Fred K. Chu for his generous gift of the pGEM recombinant plasmids, and Mr. Jung Mook Choi and Mr. Keun Soo Son for their assistance in the preparation of the manuscript.
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