Figure 3.

Structure of PrRP20 and PrRP31 and its analogs [31,55,56,58,65,67]. Blue amino acid Ser¹ marks the beginning of PrRP31 from the N-terminus. Blue amino acid Thr¹² marks the beginning of shorter isoform PrRP20 (also known as PrRP(12–31)). Blue amino acid Trp¹⁹ marks tridecapeptide PrRP(19–31) and blue Ile²⁵ marks the shortest fragment heptapeptide PrRP(25–31). Green amide group NH₂ and green Arg²³, Arg²⁶, Arg³⁰, and Phe³¹ amino acids are essential for the functionality of the peptide. Light grey amino acids mark changes of amino acids that preserved good functional activity. Dark grey Arg¹¹ could be substituted by Lys¹¹ and its secondary amino group, fatty acids, were attached through different linkers. γ-E: γ-glutamic acid, MEG-FA: multiple ethylene glycol-fatty acid (four ethylene glycol units attached to octadecanedioic acid via lysine linker incorporating carboxylated moiety), PheCl₂: (3,4-dichlor)phenylalanine, PheNO₂: (4-nitro)phenylalanine, PheF₅: pentafluoro-phenylalanine, 1-Nal, 2-Nal: napthylalanine, Phg: phenylglycine, TTDS: short chain of polyethylene glycol (1,13-diamino-4,7,10-trioxadecan-succinamic acid).