Figure 3.

NMR solution structure of recombinant melittin in TFE/water/glycerol determined from NOE data (PDB ID: 6DST) differs from the structure predicted by CS-ROSETTA. For (A) and (B), structure calculation was performed using CYANA⁴⁵ version 3.98. For (C) and (D), structure prediction based on chemical shifts was performed using CS-ROSETTA.⁵⁶ For (B) and (D), structured regions are rendered as thick ribbons, and unstructured regions are shown as cyan-colored tubes; for the structured regions, secondary structural elements were assigned by DSSP^51,52 and are indicated by color: blue for helix, green for turns, and yellow for bends. (A) Stereoview of 20 conformers showing mostly consistent C^α traces for residues ∼4−23, with frayed N- and C-termini. (B) Stereoview of the ribbon diagrams of the 20 conformers from (A). For all conformers, a continuous helical structure spans 4−23, unstructured regions are represented by residues 1 and 25−26, and a turn is assigned to residue 3. Residue 2 may form a turn (in at least 75% of conformers) or be part of an unstructured region, and residue 24 is assigned to a bend (in 50% of conformers) or an α-helix. The average bend angle of the NMR structure is 131 ± 8°. (C) Stereoview of 10 CS-ROSETTA-calculated conformers showing mostly consistent C^α traces. (D) Stereoview of the ribbon diagrams of the 10 conformers from (C). All conformers have two helices spanning residues ∼3−10 and ∼14−23, which are separated by turns and unstructured regions on residues ∼11−13. The average bend angle of the CS-ROSETTA-predicted structure is 26 ± 10°. The global C^α RMSD between the representative NOE-derived NMR structure (model 10) and the CS-ROSETTA-predicted structure (model 1) is 8.0 Å (residues 1−26). The global C^α RMSD for the structured regions (residues 3−21) after removal of the frayed ends is 16.8 Å.