Effects of amino acid substitution on the physicochemical properties of artificial proteins with random sequences

Physicochemical properties of four random proteins, each consisting of abou t 150 amino acid residues with different sequence identity, were compared t o know the correlation between the physicochemical properties and its seque nce. The results showed that the extent of the sequence alterations correla ted well with the extent of differences in CD spectra, roughly with those i n pH-solubility profiles and sedimentation velocity, and not with that in t he binding of a hydrophobic fluorescent dye (ANS). Therefore, proteins with similar sequences can have different physicochemical properties, indicatin g that the extent of mutational effects varies in response to the sequence being altered. This warrants the evolution of a protein in a sequence-speci fic manner.