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. Author manuscript; available in PMC: 2006 Jan 31.
Published in final edited form as: Nature. 2005 Nov 13;438(7067):460–465. doi: 10.1038/nature04268

Figure 3. Alternative kinetic models for RNAP translocation.

Figure 3

a, A power stroke model where translocation (δ, red) is driven by irreversible PPi release. b, A brownian ratchet model where reversible oscillation between pre- and post-translocated enzyme states can occur before NTP binding (blue). c, A brownian ratchet model where translocation and NTP binding can occur in either order. This model postulates the existence of a secondary NTP site to accommodate the possibility of nucleotide binding when the enzyme is in its pre-translocated state.