Fig. 3

The length of the second helix is highly responsible for the compaction of single-chain three-helix bundles. (Top) The blueprints of single-chain three-helix bundles. The white bars indicate the α-helices, and the black bars indicate the loop regions, where integer H denotes the variable length of the second α-helix. The alphabets beneath the loop represent the ABEGO of the loop region specified in the blueprint. (Bottom) Bar graphs to summarize the foldability of each blueprint with the variable length of the second α-helix, H, scanned from 5 to 20 residues.The bars represent the population of folded structures that showed a TM-score higher than 0.55 as referenced by ideal CW (left) or CCW (right) three-helical topologies. The vertical axis represents the length of the second α-helix H. The structures shown beside the bars are the representative snapshots from the backbone-building simulations with highest TM-scores