Isolation of rat brain myelin, monitored by polyacrylamide gel electrophoresis of dodecyl sulfate-extracted proteins

Abstract

Myelin has been isolated from total rat brain. The purification steps involved differential centrifugations and density gradient centrifugations on decreasing sucrose molarities. The purification of myelin has been monitored by polyacrylamide gel electrophoresis of SDS-extracted membrane proteins. Myelin fractions show fast-migrating basic proteins L and M, proteolipid protein U, slow-migrating protein X (probably Wolfgram protein), and other unidentified minor proteins. Protein X is found in decreasing proportions in myelin preparations which band on decreasing sucrose densities (0.88, 0.80, 0.70 M). In contrast, this component is extracted in high amounts (50%) from the supernatant of the hypo-osmotically shocked myelin banding on 0.88 M sucrose. A connection of this protein with the myelin-like fraction 2 is suggested. Sequential treatment of myelin with small volumes of low SDS concentrations extracts mostly basic proteins L and M. Proteolipid protein U and protein X are extracted with increasing SDS concentrations.