A triglyceride and cholesteryl ester transfer protein associated with liver microsomes.

An intracellular protein accelerates the transfer of triglyceride and cholesteryl ester. The fraction of phospholipid transferred was much less than for the less polar lipids. A rich source of this activity was obtained from low ionic strength washes of liver microsomes. The protein was partially purified by column chromatography on Bio-Gel A-5m and hydroxylapatite. The elution position of the transfer protein on gel filtration corresponds to a protein with a molecular weight of about 200,000. The isoelectric point of the partially purified protein is between pH 5.2 and 5.6. At each step of the purification the stimulation of triglyceride transfer was greater than that of cholesteryl ester.