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A highly processive topoisomerase I: studies at the single-molecule level
Marcin Jan Szafran1, Terence Strick2, Agnieszka Strzałka3
1Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14A, 50-383 Wrocław, Poland marcin.szafran@uni.wroc.pl.
Nucleic Acids Research
|June 2, 2014
Summary
Actinobacteria
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Type IA topoisomerases manage DNA supercoiling via strand passage.
- Actinobacteria uniquely possess only TopA, lacking typical Zn-finger motifs in its C-terminal domain.
Purpose of the Study:
- Investigate the impact of the unique C-terminal domain on actinobacterial TopA activity.
- Characterize the DNA relaxation mechanism of Streptomyces coelicolor TopA (ScTopA).
Main Methods:
- Employed real-time single-molecule experiments.
- Analyzed DNA relaxation dynamics of ScTopA.
- Studied C-terminally truncated ScTopA mutants.
Main Results:
- Discovered exceptionally high processivity in ScTopA, unprecedented for type I topoisomerases.
- Demonstrated that ScTopA processivity is modulated by torque.
- Identified a positively charged amino acid stretch in the C-terminal region linked to high processivity.
Conclusions:
- The unique C-terminal domain of actinobacterial TopA is crucial for its high processivity.
- Torque-dependent processivity suggests a role in managing DNA supercoiling under mechanical stress.
- Positively charged residues in the C-terminus likely mediate interactions essential for enzyme function.
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