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, MGF is upregulated in muscle after mechanical overload, where it supports tissue repair and growth; recombinant forms are studied for regenerative and performance-enhancement effects22138.
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, MGF is a 24-amino-acid E-peptide splice variant of IGF-1 (IGF-1Ec) produced in mechanically stressed or damaged muscle that activates IGF1R and local anabolic pathways involved in muscle repair and hypertrophy22138144.
Length and Sequence
Melanotan I is 13 amino acids long, whereas 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. 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.