Refolding of cytochrome b562 and its structural stabilization by introducing a disulfide bond.

The packing mechanism of the secondary structures (4-alpha-helices and 3(10)-helix) of cytochrome b562 is simulated by the "island model," where the formation of protein structure is accomplished by the growth-type mechanism with the driving force of packing of the long-range and specific hydrophobic interactions. Packing proceeds through the formation of the structure at the nonhelical part, where a lot of hydrophobic pairs are distributed. Consequently, conformation, nearly similar to the native one, is successfully obtained. With the help of this result, the theoretical prediction of the possibility of forming this disulfide mutant (N22C/G82C) of b562 can be performed prior to the experiments by our geometrical criterion ("lampshade"). This criterion is expected to be a significant principle for introducing possible disulfide bonds into a protein to be engineered.