Role of phospholipids in the lipophorin particles of Rhodnius prolixus.

The lipophorin of Rhodnius prolixus metabolically labelled with 32P exclusively in the phospholipid moiety was purified on a potassium bromide gradient and treated with phospholipase A2 in the presence of an excess of fatty acid-free albumin. The treatment completely removed the phospholipids from the particles and generated [32P]-lysophosphatidylcholine, [32P]-lysophosphatidylethanolamine, and free fatty acids that remained bound to albumin. The phospholipid-depleted lipophorin particles remained soluble, indicating that phospholipids are not essential in maintaining the stability of the particles in aqueous solution. Complete removal of phospholipids did not affect the association of apolipophorin III with lipophorin particles. Lipophorin density increased slightly from 1.120 to 1.134 g/ml after treatment. The phospholipid-depleted particles also retained their ability to be recognized and loaded in vitro with phospholipids delivered by the fat body, thus supporting the concept of lipophorin's role as a reusable lipid shuttle for phospholipids.