FIGURE 3.

Experimentally measured parameters (SSP and normalized CSI) for (A and B) rmMBP in 30% TFE-d₂ at 300 K, and (C and D) rmMBP in 100 mM KCl at 277 K, for comparison with (E) IDP order predictions using PONDR (VL-XT Predictor) (92,93), (F) secondary structure predictions using GOR4 (94), and (G) a visually enhanced sequence representation using hydrophobic cluster analysis (HCA) (95). The gray bars align the PONDR-predicted regions of order over all the panels. The dashed lines in panels B and D represent minimum threshold values for the formation of either α-helices (positive values), or β-strands (negative values). PONDR uses a neural network to predict regions of order/disorder in IDPs; the dashed line (E) represents the order/disorder threshold. Based on this prediction, rmMBP has three regions of order which align with the α-helical prediction from GOR4 (F). Hydrophobic cluster analysis (HCA) visually enhances primary sequence data using symbols (□, T; ⊡, S; ♦, G; ★, P), and colors (red, P and acidic residues D, E, N, Q; blue, basic residues H, K, R; green, hydrophobic residues V, L, I, F, W, M, Y; and black for all other residues, G, S, T, C, A). The hydrophobic clusters in rmMBP (G) align with both the predicted α-helices (F) and the experimentally measured α-helices (A and B), and occur within the PONDR-predicted ordered regions (E).