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, PEG-MGF is used experimentally to enhance muscle repair and hypertrophy after mechanical overload or injury by stimulating satellite-cell activation and protein synthesis6373138.
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, PEG-MGF is a poly(ethylene glycol)-conjugated form of Mechano Growth Factor (IGF-1Ec splice variant) comprising the 24-aa C-terminal E-peptide of IGF-1, designed to extend half-life while activating IGF-1 receptor–mediated anabolic signaling in muscle satellite cells637322138.
Length and Sequence
Melanotan I is 13 amino acids long, whereas PEG-MGF is longer as it has a length of 24 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. PEG-MGF is made up of a sequence of Tyrosine, Glutamine, Proline, Proline, Serine, Threonine, Asparagine, Lysine, Asparagine, Threonine, Lysine, Serine, Glutamine, Arginine, Arginine, Lysine, Glycine, Serine, Threonine, Phenylalanine, Glutamic acid, Glutamic acid, Arginine, Lysine.