Figure 8.

Active site positions of selected residues in the Mg²⁺ system (top) that contribute to the (de)stabilization of the TS during catalysis. The residues shown in red correspond to those which are common to all TSs or have a large contribution (see text). Bottom: Sequence alignment of the X family polymerases for the selected residues (highlighted in yellow). Key: “*”indicates residues conserved in all sequences,“:” indicates residues conserved in at least three of the four sequences, “.” indicates homologous residues present in at least three of the four sequences.