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Inhibition of poly(A) polymerase by rifamycin derivatives
Abstract:
The effect of several rifamycin derivatives on poly(A) synthesis in vitro was tested using purified rat liver mitochondrial poly(A) polymerase assayed with an exogenous primer. When used at a concentration of 300 mug/ml, derivatives AF/013, PR/19, AF/AETP, M/88 and AF/ABDP completely inhibited activity corresponding to 50 mug of enzyme protein. Under similar conditions, derivatives DMAO and AF/MO failed to inhibit enzyme activity. Studies with PR/19 showed that the drug interacted directly with the enzyme molecule and did not affect the enzyme-primer complex formation. The inhibition by the drug could be reversed by increasing the substrate (ATP) concentration. It is concluded that some rifamycin derivatives can specifically inhibit template-independent nucleotide chain elongation reactions.
Insights
Several rifamycin derivatives potently inhibit mitochondrial poly(A) polymerase activity in vitro. These compounds specifically block nucleotide chain elongation, offering potential for targeted therapeutic interventions.
Area of Science:
- Biochemistry
- Molecular Biology
- Pharmacology
Background:
- Mitochondrial polyadenylation plays a crucial role in gene expression regulation.
- Rifamycin derivatives are known for their diverse biological activities, including antimicrobial properties.
Purpose of the Study:
- To investigate the inhibitory effects of various rifamycin derivatives on mitochondrial poly(A) synthesis.
- To elucidate the mechanism of action of these inhibitors on poly(A) polymerase.
Main Methods:
- Purified rat liver mitochondrial poly(A) polymerase was used for in vitro assays.
- Enzyme activity was measured using an exogenous primer and varying concentrations of rifamycin derivatives and ATP.
Main Results:
- Five rifamycin derivatives (AF/013, PR/19, AF/AETP, M/88, AF/ABDP) completely inhibited poly(A) polymerase activity at 300 µg/ml.
- Two derivatives (DMAO, AF/MO) showed no inhibitory effect.
- PR/19 was shown to bind directly to the enzyme, not affecting enzyme-primer complex formation.
- Inhibition was reversible by increasing substrate (ATP) concentration.
Conclusions:
- Certain rifamycin derivatives specifically inhibit template-independent nucleotide chain elongation reactions catalyzed by mitochondrial poly(A) polymerase.
- These findings suggest a potential mechanism for targeting mitochondrial gene expression with specific rifamycin analogs.