Figure 5
Fragment-based molecular replacement of a GPCR. As a model case, the structure of β2AR was solved by molecular replacement using T4 lysozyme followed by helical fragments. (a), (b) and (c) depict 2Fo − Fc maps contoured at 1.5σ for transmembrane helix 1, which was not present in the partial MR models, with the final refined structure in green. In (a) only T4 lysozyme had been placed; in (b) seven α-helical fragments had been added and (c) shows a transmembrane helix 1 OMIT map calculated with the final refined structure. In (d), the Phaser log-likelihood gain (LLG) and Rfree after three cycles of refinement in phenix.refine are plotted as a function of the number of fragments placed. AH1 denotes the first α-helix, AH2 the second and so forth. |