In Vivo Incorporation of ³²P into Myelin Basic Protein from Normal and Quaking Mice

Summary

Myelin basic protein in normal mice is phosphorylated. Since phosphorylation can decrease the net positive charge of the myelin basic protein, this could affect molecular interactiss between this protein and other myelin components. In this study P incorporation into the small and large components of the myelin basic protein was studied in immature and young adult mice and also in Quaking mutants which have a severe myelin deficit. We found a short half-life of ³²P in myelin basic protein. The ³²P specific activity of myelin basic protein was higher in immature and Quaking mice than in young adult animal

Of the ³² P-labeled basic proteins of control and Quaking mice, the small component had a slightly higher specific activity than the large component. Although the small basic protein is quantitatively decreased in Quaking mice, the ratio of specific activity of small to large basic protein is similar in control and Quaking animals. Since Quaking and immature mice have many uncompacted myelin lamellae, these preliminary results suggest that phosphorylation and dephosphorylation could be involved in compaction mechanisms.

Supported by the Swiss National Science Foundation, grant 3.684-76 and the Swiss Multiple Sclerosis Society.