CHARACTERIZATION OF SULPHATIDE‐CONTAINING LIPOPROTEINS IN RAT BRAIN¹

Abstract

Abstract —(1) Water‐soluble [ 35 S]sulphatide is found in the 105,000 g supernatant (SN) of rat brain after intraperitoneal injection of Na 2 35 SO 4 . This labelled sulphatide has a density between those of free lipid and free protein. (2) Fractionation of SN by preparative acrylamide gel electrophoresis indicates that the [ 35 S]sulphatide is not distributed among all SN proteins, but is associated with certain specific proteins. One of the isolated [ 35 S]sulphatide‐containing proteins appears homogeneous by analytical acrylamide gel electrophoresis at several pH values. (3) Comparison of the turnover of [ 35 S]sulphatide in microsomes, SN, and myelin indicates that these three subcellular fractions behave as distinct metabolic pools, which meet the requirements for a precursor‐product relationship between microsomes and SN and between SN and myelin. (4) These results suggest that sulphatide, synthesized in the microsomes, is transported to the myelin membrane as water‐soluble sulphatide containing Iipoproteins in SN.