Figure 4
Re-refinement of PDB entry 3cmc demonstrates how automated LSSR pruning avoids model disruption where NCS copies have distinct but similar conformations. 3cmc is the 1.77 Å resolution structure of GAPDH determined by Moniot et al. (2008) with fourfold NCS. (a) shows how BUSTER refinement with the -autoncs_noprune option produces difference density (contoured at 3σ) close to His142 in the P chain (cyan with atom colouring). This is because LSSR forces a consensus conformation between the residue and its NCS equivalents, shown as superposed `ghosts' in magenta, orange and yellow. (b) Using the -autoncs option means that this residue is `pruned' from the restraint lists and can adopt distinct conformations in the NCS copies nestling into the 2Fo − Fc density (shown in grey contoured at 1.2σ). |