A model, based on amino acid sequence data, is proposed for the organization of the myelin proteolipid in myelin membrane. The model has three distinctive features: three trans-membrane segments that traverse the lipid bilayer, two cis-membrane domains that enter and exit the same side of the membrane, and a highly charged segment resembling myelin basic protein on the cytoplasmic side of the membrane. It is proposed that the cis-membrane domain(s) can promote the formation and stabilization of the multilamellar myelin structure by hydrophobic interaction with the apposite bilayer across the extracellular space.

Amino Acid Sequence↗

PubMed1984

Structural analogies between myelin basic protein and proteolipid.

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Amino Acid Sequence↗

PubMed1983

Amino acid sequence of bovine white matter proteolipid.

The sequence of the bovine white matter proteolipid has been studied by a combination of proteolytic digestion and chemical cleavage at tryptophan residues. Alignment of peptides obtained by digestion with trypsin, chymotrypsin, clostripain, and Staphylococcus aureus protease gave the sequence of 52 residues at the amino terminus, 96 residues at the carboxyl terminus, and several additional segments. Peptides obtained by treatment of the protein with 2-(2-nitrophenylsulfenyl)-3-methyl-3'-bromoindolenine confirmed the alignment and extended the sequence. This information, combined with that of other investigators, permits us to propose the primary structure for the entire protein. On the basis of the sequence determination, the molecular weight of the proteolipid protein is 29,869.

Amino Acid Sequence↗

PubMed1983

Gene duplication in bovine brain myelin proteolipid and homology with related proteins.

Analysis of the amino acid sequence of bovine brain myelin proteolipid reveals not only extensive internal homology, but also homology with portions of the myelin basic protein, the peripheral nerve myelin protein, Po, and with the small proteolipid subunit of mitochondrial ATP synthase. These results suggest that the myelin proteolipid gene has been constructed from a small number of genetic elements, and that these elements are also found in non-myelin proteins. Furthermore, the proteolipid appears to have evolved by acquisition of elements from a 'gene pool' over a period of time, rather than by a simple duplication mechanism.

Amino Acid Sequence↗