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. Author manuscript; available in PMC: 2015 Nov 12.
Published in final edited form as: Curr Opin Struct Biol. 2010 Dec 24;21(1):83–91. doi: 10.1016/j.sbi.2010.12.001

Figure 5.

Figure 5

Comparison of Pol A family and Pol B family in the pol site Pol A and Pol B members enforce W-C complementarity between the templating nucleotide and incoming nucleotide differently. In Pol γ (and T7 RNAP), they are accomplished by two sets of check-point residues in the minor groove: E895 and N1098 (E480 and N611) before translocation and R853 and Q1102 (R429 and Q615) after translocation, respectively. In RB69, both bps can be ensured by three tyrosines (Y416, Y564 and Y391) that are conserved in Pol α and Pol δ. The latter arrangement may be the more efficient and rigorous. Deoxyribose selection is conferred in part by Y951 on the O-helix of the fingers domain. The Y951F substitution in Pol γA reduces ddCTP incorporation by 5000 fold [53].