Characterization of Wolfgram proteolipid protein of bovine white matter and fractionation of molecular weight heterogeneity

Abstract— Wolfgram proteolipid protein fraction (WPF) was prepared as the insoluble pellet resulting from the extraction of myelin three times with chloroform-methanol (CM, 2:1, v/v). Amino acid composition analysis showed that the WPF described here is comparable to that described by Wolfgram (1966) and by Eng et al. (1968). Disc gel electrophoresis in two different buffer systems revealed three major protein bands, W1, W2 and W3, having apparent mol. wt of 23,500, 54,000 and 62.000 daltons respectively. The 54,000–62,000 doublet is stable to performic acid oxidation and to reduction with β-mercaptoethanol. Characterization of WPF by sedimentation velocity revealed two peaks having S_{20, w} values of 1 96 and 0 84. In comparison, water soluble Folch-Lees proteolipid apoprotein (APL) prepared in this laboratory (Hendrickson et al., 1972) differs from WPF in its amino acid composition and in its behavior on disc gels and in the ultracentrifuge. We employed preparative electrophoresis on polyacrylamide gels containing sodium dodecyl sulphate (SDS) in order to separate and purify heterogeneous components observed in WPF. We obtained a fraction containing essentially pure W1 protein and determined that it has a unique amino acid composition. Various fractions containing partly purified high molecular weight components were also recovered. Gel filtration chromatography on columns of Sephadex G-200 was also successfully employed in this study of WPF.