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. Author manuscript; available in PMC: 2016 Dec 29.
Published in final edited form as: JSM Biochem Mol Biol. 2016 May 30;3(1):1013.

Figure 2.

Figure 2

Proposed translocation mechanisms of hexameric helicases. Replicative helicases are hexameric rings composed of an N-tier and C-tier; the motor domains are in the C-tier. a) Inchworm mechanism. Left: the C- and N-tiers are parallel and compact. Middle: The C-tier opens at one interface and expands into a spiral structure, melting DNA and leaving the N-tier a flat uninterrupted ring. Right: The C-tier reassumes the compact shape and translocates the N-tier on DNA. b) Rotary model. Left: The C-tier is shaped as a spiral lock washer and connects to a flat N-tier ring. Middle: ATP hydrolysis translates the lock washer shape by one protomer, resulting in DNA translocation. Right: ATP hydrolysis translates the lock washer shape by one protomer, resulting in DNA translocation.