Prion Proteins: Evolution and Preservation of Secondary Structure

Prions cause a variety of neurodegenerative disorders that seem to result from a conformational change in the prion protein (PrP). Thirty‐two PrP sequences have been subjected to phylogenetic analysis followed by reconstruction of the most probable evolutionary spectrum of amino acid replacements. The replacement rates suggest that the protein does not seem to be very conservative, but in the course of evolution amino acids have only been substituted within the elements of the secondary structure by those with very similar physico‐chemical properties. Analysis of the full spectrum of single‐step amino acid substitutions in human PrP using secondary structure prediction algorithms shows an over‐representation of substitutions that tend to destabilize α‐helices.