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Structure and mechanism of hexameric helicases
Barbara Medagli1, Silvia Onesti
1Structural Biology, Sincrotrone Trieste (Elettra), Area Science Pk, Basovizza, Trieste, Italy, barbara.medagli@elettra.trieste.it.
Advances in Experimental Medicine and Biology
|November 20, 2012
Summary
Hexameric helicases, crucial for DNA replication and repair, utilize conserved ATP-binding engines (ASCE) with RecA-like or AAA+ folds. These ring structures facilitate efficient DNA unwinding via ATP hydrolysis.
Area of Science:
- Molecular Biology
- Biochemistry
- Structural Biology
Background:
- Hexameric helicases (SF3-6) are vital for DNA replication, repair, and RNA metabolism.
- They possess a conserved core engine (ASCE), a P-loop NTPase subdivision, essential for ATP hydrolysis.
- Two main variants exist: RecA-like (SF4, SF5) and AAA+ fold (SF3, SF6).
Purpose of the Study:
- To elucidate the conserved mechanisms of hexameric helicases.
- To understand how ATP hydrolysis powers mechanical work in these enzymes.
- To explore the structural basis for their role in DNA unwinding.
Main Methods:
- Biochemical assays
- Biophysical studies
- Structural data analysis
Main Results:
- NTP-binding sites at subunit interfaces amplify small ATP-site changes into large movements.
- The toroidal ring structure encircles nucleic acids, enhancing enzyme stability and processivity.
- RecA-like and AAA+ fold motors show convergent mechanisms for coupling ATP hydrolysis to nucleic acid movement.
Conclusions:
- Hexameric helicases are essential molecular machines with conserved functional principles.
- Their ring structure and ATP-binding engines are key to efficient DNA unwinding.
- Convergent evolution has led to similar mechanisms for ATP-driven nucleic acid translocation.
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