Peripheral nervous system myelin and Schwann cell glycoproteins: Identification by lectin binding and partial purification of a peripheral nervous system myelin-specific 170,000 molecular weight glycoprotein

Radioiodinated lectins were used to detect glycoproteins of peripheral nervous system (PNS) myelin (rat, human, bovine) and cultured rat Schwann cells. Proteins were resolved by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis and transferred to nitrocellulose filters. The filters were overlaid with radioiodinated lectins of known saccharide affinities. These included concanavalin A, Helix pomatia, Limulus polyphemus, Maclura pomifera, peanut, soybean, Ulex europaeus, and wheat germ agglutinins. Inclusion of the appropriate monosaccharide in the overlay solution (0.2 M) inhibited lectin binding to the nitrocellulose-fixed proteins. Fluorography permitted identification of 26 myelin glycoproteins and many more in Schwann cells. All lectins labeled a band present in myelin, but not Schwann cells, corresponding to the major PNS myelin protein, P₀. Our attention focused on a high-molecular-weight myelin glycoprotein [apparent molecular weight [M(r)] 170,000], which appeared abundant by Coomassie Blue staining and which was heavily labeled by all lectins except concanavalin A. A protein with approximately this M(r) and lectin-binding pattern was present in human and bovine PNS myelin as well, but not detected in rat Schwann cells, CNS myelin, liver and fibroblast homogenates, or cultured bovine oligodendroglia. Hence this 170,000 M(r) glycoprotein is apparently unique to PNS myelin.