In vivo acylation of rat brain myelin proteolipid protein.

Examination of brain myelin proteins by sodium dodecyl sulfate-gel electrophoresis followed by fluorography clearly showed that both proteolipid protein (PLP) and DM-20 were acylated 24 h after the intracerebral injection of 30-day-old rats with [3H]palmitic acid. The radioactivity associated with PLP remained after purification, re-electrophoresis, and fluorography. Most of the radioactivity associated with PLP was removed when the gels were treated with hydroxylamine and then fluorographed, indicating that fatty acids were bound to PLP by ester linkage. Cleavage of purified PLP with methanolic sodium hydroxide readily released almost all protein-bound radioactivity. Thin layer chromatography of this material on both silver nitrate and reverse-phase plates provided evidence that most of the radioactivity co-migrated with methyl palmitate (77%) and methyl stearate (19%); however, some radioactivity was associated with methyl oleate (4%). Gas-liquid chromatography of the fatty acids associated with PLP distinctly revealed the presence of methyl palmitate and a detectable peak of methyl stearate.