Octapeptide repeat region

Fig. 1 Diagram of the human prion protein gene showing the octapeptide repeat region (51-91), regions of predicted secondary structure [designated a (helical) or [3 (sheet)], pathogenic or likely pathogenic mutations (above in red), non-synonymous polymorphisms and synonymous polymorphisms (below in green)...

The octapeptide repeat region is not required for the conversion of Prpc pj.pSc propagation of the disease process. Nevertheless, extra-repeat insertional mutations in one PRNP allele trigger disease. It is conceivable that disorder of copper binding in these extended protein species might feature in the formation of altered PrP isoforms and/or PrP aggregation. In this regard, it is noteworthy that PrP is... 

Lee, D. C., Sakudo, A., Chi-keyong, K., Nishimura, T., Saeki, K., Matsumoto, Y., Yokoyama, T., Chen, S. G., Itohara, S., and Onodera, T. 2006. Fusion of Doppel to octapeptide repeat and N-terminal half of hydophobic region of prion protein confers resistence to serum deprivation. Microbiol. Immunol. 50 203-209... 

Fig. 2. Sequence content of spa repeats at nucleotide and amino acid levels. Repeats differing at the nucleotide level may be identical at the amino acid level. Identical codons are depicted using the same colors equivalent codons corresponding to synonymous mutations are colored with similar hues. The translated sequence reveals a conserved octapeptide motif comprised almost exclusively of charged amino acids and is suggestive of a surface-exposed loop region with repeating turns. Repeats Tl-Zl bear a single codon insertion between positions 1 and 2 most common spa types begin with one of these repeats, such that the initial repeat is usually 27-bp in length (vs. 24-bp).

---