... state may bemaintained mainly by key amino acids. In this study, two point-mutatedproteins each with a single base substitution [alanine for tryptophan(W14 0A) and alanine for lysine (K13 3A) ] and ... than that of the wild-type pro-tein. Therefore, some or all of the residues in the 127–149 segment are critical for maintenance of the nativeconformation of the protein. In addition, Griko andcoworkers ... Two point-mutated proteins, with a singlebase substitution of alanine for tryptophan (W14 0A) and alanine for lysine (K13 3A) , and two truncatedfragment proteins, with fragments 1–139 [SNase(1–139)...