Sequence-to-structure relation in proteins-amyloidogenic proteins with chameleon sequences

The existence of polypeptide chain fragments in which identical sequences translate into different secondary folds gives rise to questions concerning the structural variability associated with amyloidogenesis. In this paper the structural contribution of identical sequences to a common hydrophobic core is assessed on the basis of the fuzzy oil drop model. The model compares the observed hydrophobicity density distribution in a protein molecule to its idealized counterpart, where all hydrophilic residues are exposed on the surface while all hydrophobic residues are internalized. The conformational variability of such fragments is thought to be associated with their role: they either participate in the formation of a stable core, or become involved in mediating the protein’s biological function. The fuzzy oil drop model provides clues as to the role of chameleon sequences in prions, seen as potential loci of conformational changes resulting in amyloidogenesis.