3D-models of consecutive MR repeats. (A) Initial model of three consecutive human MR repeats (T11 to T13, aa: 306-339). β-strands, turns and inter-repeat regions are colored in yellow, green and magenta, respectively. For clarity, only the side chains of residues discussed in the text are shown (stick models). The consensus sequence motifs, SSV and SPxN, are indicated. (B) Models resulting from the MD simulations. The dominant cluster of the last 50 ns of the REMD replica at 303 K and the most populated cluster of the last 30 ns of the solvated 50 ns MD simulation are shown in orange and green, respectively. (C) Final model (energy minimized) of five consecutive human MR repeats (T9 to T13, aa: 280-338) after the 20 ns MD simulation in explicit water. The β-turn structure corresponding to the SPxN motif is colored in orange. (D) Cross-section of the resulting β-helix core of the model shown in C (at repeats T10, T11). Similar residues forming ladders discussed in the text are labeled. Hydrogen bonds are indicated by dashed lines in blue. The molecular model illustrations of this figure were rendered using PyMOL.