Structure and molecular arrangement of proteolipid protein of central nervous system myelin

摘要: Proteolipid protein (PLP) of central nervous system myelin is one the most hydrophobic integral membrane proteins. It consists a 276-residue-long polypeptide chain with five strongly sequences 26, 30, 39, 12, and 36 residues, respectively, linked by highly charged hydrophilic sequences. Hyposmotically dissociated bovine membranes were treated trypsin. PLP was completely cleaved into smaller fragments, whereas basic remained essentially unaltered. The proteins tryptic peptides separated after removal short, water-soluble three large fragments 11, 7.3, 9.0 kDA, respectively. They characterized their molecular mass NH2-terminal amino acid sequences, which proved that trypsin predominantly at Arg-97 yielding 11-kDa fragment from Gly-1 through Arg-97, Arg-126 releasing 7.3-kDa Gly-127 Lys-191, Lys-191 9-kDa Thr-192 Phe-276. We propose integrated lipid bilayer NH2 terminus positively loops oriented toward extracytosolic side membrane, negative loop COOH cover cytosolic bilayer. Basic remains protected against cleavage, indicates its apposition to membrane. These cleavage sites support suggested orientation in thereby extend our knowledge about arrangement components this In demyelinating processes desintegration could be initiated proteolysis external surfaces proteolipid similar way as described here.