[A protein that accounts for more than half of the peripheral nervous system myelin protein. The extracellular domain of this protein is believed to engage in adhesive interactions and thus hold the myelin membrane compact. It can behave as a homophilic adhesion molecule through interactions with its extracellular domains. (From J Cell Biol 1994;126(4):1089-97) ( MSH )] (UMLS (CSP) C0071316) =Amino Acid, Peptide, or Protein; Neuroreactive Substance or Biogenic Amine ;