To examine the relative importance of the stability of secondary structure and the hydrophobicity of the sequence in determining the mechanism of protein folding, solvent-exposed residues in the four-helical protein Im9 were altered by mutagenesis.i The ribbon diagrams depict residues altered to tailor secondary structure (left) or hydrophobicity (right). The results show that intermediates are stabilized both by increasing helix propensity and by increasing hydrophobic contacts between helices, supporting a diffusion-collision model for immunity protein folding. For further details, see Cranz-Mileva et al., pages 41-50.
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