Amino acid analysis and N—terminal sequence determination of P7 proteolipid apoprotein from human myelin

Abstract

There is a general agreement that myelin from central nervous system has a relatively simple protein composition, which makes it an excellent material for protein-lipid interaction studies in a membrane. Three main protein types have been described: basic proteins, proteolipid proteins and acidic Wolfgram proteolipid proteins (see ref. [l] for review). The distribution ratio between these proteins is variable depending on the procedures used [2-51 and animal species examined [2,6,7]. In human myelin, most work has been devoted to the unique basic protein [8-lo], and a sequence has been published [ 11 ,121. To our knowledge no comparable information is available for the other proteins; so, during the course of the sequence study of the major rat brain myelin proteolipid P7 protein [ 131, we also decided to elucidate the primary structure of the corresponding human protein. This was done in order to provide information of possible homology in protein sequence of the proteolipid apoprotein during evolution. In the present paper, we present results concerning the amino acid composition and the sequence of the first 20 amino acids of the N-terminal moiety.