Function
While Melanotan I is approved in some regions for prevention of phototoxicity in erythropoietic protoporphyria and is studied as a skin-darkening, photoprotective peptide3444, Snap-8 is a cosmetic peptide studied for reducing wrinkle depth by inhibiting synaptic vesicle fusion and subsequent muscle contraction in facial expression muscles5060.
Mechanism
While Melanotan I works as a linear 13-amino-acid analog of α-MSH (afamelanotide) that selectively activates MC1R on melanocytes, increasing eumelanin synthesis and providing photoprotection3444, Snap-8 is acetyl octapeptide-3 (Ac-Glu-Glu-Met-Gln-Arg-Arg-Ala-Asp-NH2), an extended analog of Argireline derived from the N-terminal region of SNAP-25 that competes with native SNAP-25 for binding to syntaxin-1, forming a non-functional SNARE complex and reducing neurotransmitter release5060.
Length and Sequence
Melanotan I is 13 amino acids long, whereas Snap-8 is shorter as it has a length of 8 amino acids. Melanotan I is made up of a sequence of Serine, Tyrosine, Serine, Nle, Glutamic acid, Histidine, Phenylalanine, Arginine, Tryptophan, Glycine, Lysine, Proline, Valine. Snap-8 is made up of a sequence of Glutamic acid, Glutamic acid, Methionine, Glutamine, Arginine, Arginine, Alanine, Aspartic acid.