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. Author manuscript; available in PMC: 2023 Jan 23.
Published in final edited form as: Crit Rev Biochem Mol Biol. 2021 Aug 17;56(6):621–639. doi: 10.1080/10409238.2021.1954597

Fig. 6: Power stroke vs. Brownian ratchet unwinding mechanisms.

Fig. 6:

A. In the power stroke model, ATP hydrolysis by the helicase is tied to conformational changes that actively push it forward into a duplex, forcibly splitting paired bases to unwind the substrate. B. Passive unwinding involves local fraying of base pairs due to thermal or torsional fluctuations that expose ssDNA, which the helicase then captures through an ATP-dependent movement.