Figure 7.

The structural mechanism for substrate specificity at −2′ position in A3s. A representative frame from MD simulations for (A) A3B-CTD (pink), (B) A3G-CTD (yellow) are used to show the molecular interactions between −2′ nucleotide and A3s. The residues that have molecular interactions with −2′ nucleotide base are shown as sticks. ssDNA is shown as orange sticks except −2′ nucleotide, which is colored in blue. −2′, −1′ and 0′ positions as well as the residues contacting −2′ nucleotide are labeled.