Isolation of basic protein-acidic lipid complex from myelin.

When lyophilized myelin prepared from canine brain white matter was extracted with a solvent mixture of n-propanol-n-hexane (2:3, v/v), it was found that the extract contained less amounts of sulfatide and phosphatidylserine and no protein like so-called proteolipid-protein in comparison with the total chloroform-methanol (2:1, v/v) extract of myelin. Thus, the propanol-hexane myelin residue was re-extracted with chloroform-methanol (2:1, v/v) and the extract was subjected to UV-spectroscopy, TLC and slab SDS-gel electrophoresis, respectively. The UV-absorption pattern of the extract showed a maximum band due to protein at about 280 nm. The lipid portion was found to be predominantly sulfatide (63.6%), phosphatidylserine (26.2%) and other lipids (10.2%), while the major portion of protein was basic protein. The amino acid composition of the extract was also very similar to that of a control porcine basic protein. The major normal fatty acids of sulfatide were C24:0 (34.5%), C24:1 (13.7%), C23:0 (8.3%) and C18:0 (16.0%), while the hydroxy acids were predominantly C24:0 (44.1%), C24:1 (22.2%) and C23:0 (10.4%). Also, the fatty acids of phosphatidylserine were mainly C18:0 and C18:1. The solubilization of the basic protein-acidic lipid complex (about 2.56 by weight in the ratio of protein to lipid) in chloroform-methanol suggested the interaction of the basic protein with acidic lipids which might be related to the molecular organization in myelin. The basic protein-acidic lipid complex was also found to have an encephalitogenic activity which seemed to be a little different from that of basic protein itself.