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. Author manuscript; available in PMC: 2018 Aug 18.
Published in final edited form as: Annu Rev Biochem. 2018 Mar 1;87:239–261. doi: 10.1146/annurev-biochem-062917-012405

Figure 7.

Figure 7

sGRS by the X-family polymerases. (a) Primary structures of Pol β, λ, μ and TdT. (b) Crystal structure of the Pol β-DNA-dNTP complex (PDB: 2FMS). Domains are labeled according to the right-hand convention. In the left-hand definition, finger and thumb would be swapped. (c) Gap filling synthesis and dRP removal by Pol β. The two DNA segments are at ~90° angle. (d) Pol λ can bridge two DNA ends by one base pair and incorporate a dNTP to match the trans template. (e) Structure of TdT bridging two DNA ends without base pairing (PDB: 4QZB). (f) Pol μ can bridge two DNA ends by a mismatched base pair and incorporate a dNTP that matches the trans template. Loop1 insertion in TdT and Pol μ segregates the two base pairs in the active site from upstream DNA.