Comparison of the major proteins of shark myelin with the proteins of higher vertebrates.

On gel electrophoresis in dodecyl sulphate solutions shark CNS myelin showed four bands close in mobility to the proteolipid protein of bovine CNS myelin. They had apparent molecular weights of 21,000, 26,000, 27,000, and 31,500. Unlike bovine proteolipid protein, all of these shark proteins were shown to be glycosylated by staining gels with the periodate-Schiff reagent. Amino acid analyses of the polypeptides eluted from polyacrylamide gels indicated a high content of apolar amino acids and a composition approximating that of the Po protein of bovine peripheral nervous system (PNS) myelin, rather than that of the CNS proteolipid protein. The shark polypeptide of apparent molecular weight 31,500 was obtained by elution from dodecyl sulphate gels and antibodies raised against it in rabbits. By probing of electroblots with this antiserum the four shark CNS bands were shown to share common determinants with each other, with a major shark PNS protein and with sheep and chicken major PNS glycoproteins (Po). The binding of antibody was unaffected by deglycosylation of the shark CNS polypeptides with anhydrous hydrogen fluoride. Together, these results appeared to establish that shark CNS myelin contains four proteins that are closely related to a major shark PNS protein and to the Po protein of higher species.