Protein methylation : Enzymology and Biological Significance of Myelin Basic Protein Methylation

Abstract

Myelin is a membrane characteristic of the nervous tissue and functions as an insulator to increase the velocity of the stimuli being transmitted between a nerve cell body and its target. Myelin isolated from human and bovine nervous tissue is composed of approximately 80% lipid and 20% protein, and 30% of the protein fraction constitutes myelin basic protein (MBP). MBP has an unusual amino acid at Res-107 as a mixture of N^(G)-monomethylarginine and N^(G), N^(G)-dimethylarginine. The formation of these methylarginine derivatives is catalyzed by one of the subtypes of protein methylase I which specifically methylates Res-107 of this protein. Several evidences are presented to demonstrate an involvement of this biological methylation in the integrity and maintenance of myelin