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. Author manuscript; available in PMC: 2018 Jul 17.
Published in final edited form as: Nature. 2018 Jan 17;553(7688):295–300. doi: 10.1038/nature25440

Figure 5. Mechanism of promoter opening and DNA melting in Pol III.

Figure 5

Schematic drawing of the promoter opening. Initially, the closed DNA is bent away by the C82 cleft loop and the clamp, while the Bdp1 tether and C34 WH1 and WH2 are disordered. Opening of the clamp allows the closed DNA to slide between clamp and lobe. Subsequently, C34 WH1 and WH2 become ordered and enclose double-stranded DNA. Closing of the clamp leads to the downwards movement of the cleft loop and DNA melting, while establishing stabilizing interactions between the Bdp1 tether and C34 WH1 and WH2. The non-template strand is stabilized by Pol III subunits C34 and C82; the template strand is presumably stabilized by the Brf1 linker.