Phosphorylation Sites of Bovine Brain Myelin Basic Protein Phosphorylated with Ca²⁺-Calmodulin-Dependent Protein Kinase from Rat Brain

Abstract

The phosphorylation sites of myelin basic protein from bovine brain were deter-mined after phosphorylation with Ca²⁺-calmodulin-dependent protein kinase. Four phosphorylated peptides were selectively and rapidly separated by reversed-phase high-performance liquid chromatography. Partial sequencing of the phosphorylated peptides by automated Edman degradation revealed that Ca²⁺-calmodulin-dependent protein kinase phosphorylated serine-16, serine-70, and threonine-95 specifically, as well as serine-115, which is located on the experimental allergic encephalitogenic determinant of the protein. Of the four amino acid sequences determined, two sequences surrounding phosphorylated amino acids, -Lys-Tyr-Leu-Ala-Ser(P)₁₆-Ala-and -Arg-Phe-Ser(P)₁₁₅-Trp-Gly-, have both sides of each phosphoserine residue occupied by hydrophobic amino acids, and a basic amino acid, arginine or lysine, is located at the position 2 or 4 residues amino-terminal to the phosphoserine residue. In contrast, the two other sequences surrounding phosphorylated amino acids, -Tyr-Gly-Ser(P)₇₀-Leu-Pro-Glu-Lys- and -Ile-Val-Thr(P)₉₅-Pro-Arg-, have a basic amino acid at the position 2 or 4 residues carboxyl-terminal to the phosphoamino acid residue.