Radar chart deviation analysis of prion protein amino acid composition defines characteristic structural abnormalities of the N-terminal octa-peptide tandem repeat.

Analysis of the amino acid composition of prion protein using a newly developed program for radar-chart deviation analysis has identified an abnormality or irregularity of the N-terminal flexible domain. Aromatic amino acids Trp and His together with Gly are abnormally abounding in this N-terminal domain, in which octapeptide GQPHGGGW is connected four times in tandem. This tetrarepeat structure has been suggested to be essential for the prion protein not only to play an intrinsic functional role in the physiological condition, but also to bring on structural abnormalities in prion disease.