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. Author manuscript; available in PMC: 2020 Feb 1.
Published in final edited form as: Semin Cell Dev Biol. 2018 Mar 28;86:92–101. doi: 10.1016/j.semcdb.2018.03.018

Figure 6.

Figure 6

Synthesis at a nick in dsDNA is facilitated by gp2.5. WT T7 DNA polymerase is unable to initiate DNA synthesis at a nick in dsDNA. Top panel: T7 DNA polymerase idles at the nick by alternating between 3’-5’ exonuclease and nucleotide polymerization activities. An interaction between gp2.5 and T7 DNA polymerase allows limited strand-displacement synthesis. This interaction is mediated, in part, by the C-terminal phenylalanine of gp2.5. In addition, gp2.5 likely stabilizes the ssDNA produced. Bottom panel: The helicase hexamer assembles on the displaced 5’-single-stranded tail when it is sufficiently long, and displaces gp2.5. Helicase and T7 DNA polymerase form a stable complex and continue DNA synthesis.