Abstract
The exercises of de novo protein design have shown that a unique structure is very difficult to attain. As the determinants of structural uniqueness in native proteins, we propose a negative factor, namely, the decrease in the side-chain conformational entropy, which can suppress the structural diversity, and can destabilize the intermediate folding state. A small globular protein, c-Myb R3, includes Ile residues on each of the three helices, respectively. These Ile residues were changed to Leu residues, to investigate the role of a β-branched amino acid in an α-helix for structural uniqueness.
