PARTIAL CHARACTERIZATION OF BASIC PROTEINS OF CHICKEN, TURTLE AND FROG CENTRAL NERVOUS SYSTEM MYELIN

Myelin basic proteins were isolated from CNS tissues of chicken, turtle and frog and compared with the corresponding protein of bovine origin. At acid pH all four proteins had comparable mobilities in polyacrylamide gels. Upon electrophoresis at alkaline pH the submammalian proteins, like the bovine protein, were separated into multiple components. The components of the chicken and frog proteins had exceptionally high and low mobilities, respectively, while those of the turtle protein had mobilities comparable to those of the bovine protein. The chicken and turtle proteins were similar to the bovine protein in amino acid composition except for containing considerably more serine and valine and having higher proportions of histidine to lysine. The frog protein differed further in having an unusually high content of tyrosine (approx 9 mol/mol protein), an unusually high arginine: glycine ratio (1.09) and practically no methylated arginine (0‐0.036 mol/mol protein). Like those of mammalian origin, the submammalian proteins each contained a single tryptophan and two methionines. Arginine, serine and glycine together accounted for approximately 40 per cent of the residues in each protein. The chicken and turfle proteins each contained roughly equal amounts of NG‐monomethyl‐ and NG, NG‐dimethylarginine, the two derivatives together comprising 0.5‐0.6 mol/mol protein. No NG, NG‐dimethylarginine was detected in any of the proteins examined. The microheterogeneity observed in the chicken and turtle proteins upon electrophoresis at alkaline pH was reproduced upon alkaline pH chromatography on carboxymethylcellulose. Chromatographic fractions of the chicken protein which differed electrophoretically at alkaline pH had virtualy identical amino acid compositions and apparent molecular weights and all contained comparable amounts of both NG‐monomethyl‐ and NG, NG‐dimethylarginine. Treatment of the submammalian proteins with BNPS‐skatole yielded two fragments comparable in size, charge and staining characteristics to those similarly produced from the bovine protein (residues 1‐116 and 117‐170). Fragments produced from the frog protein by treatment with BrCN were comparable in size and charge to those similarly produced from the bovine protein; those produced from the chicken and turtle proteins were much different. In immunodiffusion studies the submammalian and bovine proteins showed reactions of identity when tested against rabbit anti‐chicken basic protein serum.