Specific interaction of central nervous system myelin basic protein with lipids effects of basic protein on glucose leakage from liposomes

Abstract

The leakage from liposomes preloaded with glucose was continuously monitored in a Perkin-Elmer Model 356 dual beam spectrophotometer using an enzyme-linked assay system. The central nervous system myelin basic protein (A1 protein) caused a 3–4-fold increase in the rate of leakage from liposomes prepared from either central or peripheral nervous system lipids and also from an egg lecithin-5% phosphatidic acid mixture. Some basic proteins, lysozyme, cytochrome c, two peripheral nerve myelin basic proteins, trypsin and the tryptic peptides derived from the A1 protein did not alter glucose leakage from the central nervous system lipid mixture. Other basic proteins, poly -lysine, profamine sulphate and a reduced “arginine-rich” histone from bull sperm had a “lytic action” on these liposomes.

Basic proteins derived from both central and peripheral nervous myelin reduced the poly -lysine-stimulated leak of the centerl nervous system liposomes whereas lysozyme had no effect. Additional evidence suggesting a strong interaction of the A1 protein with liposomes was provided by studies of the action of trypsin on the liposome-protein complexes. The glucose leak of central and peripheral nervous liposomes complexes with A1 protein was reduced by incubation with trypsin, but was still significantly higher than leakage of these liposomes before the addition of the A1 protein.