The alignments were prepared using PROMALS3D multiple sequence and structure alignment server (Pei et al., 2008). The following protein structures were used for the alignments: 6q4u - Thermus aquaticus Taq polymerase residues 423–832; 1l5u - Geobacillus stearothermophilus DNA Pol I residues 469–876; and 1kln - E. coli DNA Pol I residues 520–918. A structural model of CCPol was prepared with I-Tasser (Yang et al., 2015). The polymerase sequences corresponding to the exonuclease domains absent from CCPol were removed from the alignment. The sequences are colored as follows: red – alpha helix, blue – beta strand, gray –E. coli Pol I thumb residues disordered in the structure used. Consensus amino acids are shown in below the structure, with conserved amino acids in bold and uppercase; aliphatic residues (I, V, L): green l; aromatic residues (Y, H, W, F): green @; hydrophobic residues (W, F, Y, M, L, I, V, A, C, T, H): green h; alcohol residues (S, T): o; polar residues (D, E, H, K, N, Q, R, S, T): p; tiny residues (A, G, C, S): t; small residues (A, G, C, S, V, N, D, T, P): s; bulky residues (E, F, I, K, L, M, Q, R, W, Y): b; positively charged residues (K, R, H): blue +; and charged residues (D, E, K, R, H): c. Consensus secondary structures are marked with pink h for alpha helix and blue e for beta strand. Polymerase domains (Thumb, fingers, and palm) are marked underneath the alignment. Predicted mechanistically important residues are marked with red asterisks (with a grey asterisk marking a CCPol alanine residue which in other PolA-like polymerases is invariably a catalytic glutamic acid) above the sequence.