Fig. 4

The structure of HBV-RT4/DNA-RNA/TFV-DP and the active site Mg ²⁺ network in comparison with that from the HIV-RT/DNA-DNA/TFV-DP crystal structure. a The HBV-RT4/DNA-RNA/ TFV-DP structure model is shown in cartoon with each domain in different color (N-terminal: orange; fingers: purple; thumb: red; palm: green; dsDNA: silver). The substrate TFV-DP and the residues involved in direct interaction with it are in stick and ball representation; b The active site configuration of the HBV-RT4/DNA-RNA/TFV-DP model. The non-bonded interactions are explicitly represented as black dashed lines as the two H-bonds (Hb1 and Hb2), and the ionic bonds formed between the Mg²⁺ ions (in red ball representation without labeling) and the chelating oxygen atoms. The water oxygen atoms participating in the chelation are labeled as from W1 to W4; c The active site configuration of the HIV-RT/DNA-DNA/TFV-DP crystal structure, only one Mg²⁺ is identified in the active site and no water molecule is involved. The hydrogen atoms are hided in the representations for clearance