Fig. 7: Hidden pol λ fidelity mechanisms.

Panels display structural intermediates corresponding to the stage of nucleotide incorporation indicated below. Ligands observed at each stage of reaction are indicated above the central panels. “Closed” and “Deformed” refer to the state of the polymerase in matched and mismatched insertion, respectively. Regions of the protein or DNA shaded from white (0 Å) to red (1 Å and above) display differences in positions of backbone C_α atoms compared to the previous intermediate (RS compared to GS, PS compared to RS, and PS_ES compared to PS). Shading of the mismatched ground state complex from white (0 Å) to red (1 Å and above) reflects differences in C_α positions compared to the matched ground state ternary complex. The catalytic (Me_c), nucleotide (Me_n) and product metals (Mn_p) are indicated by spheres colored according to metal identity (Ca²⁺, yellow; Na⁺, orange; Mg²⁺, green; Mn²⁺, magenta). Protein subdomains are labeled as the N (thumb), C (palm), D (fingers) and L (lyase) domains. Superimposition and shading was performed with the program Chimera by overlaying the palm domains (residues 386–494) of each structure.