A discoidal lipoprotein from the coelomic fluid of the polychaete Nereis virens

A discoidal lipoprotein was isolated from the coelomic fluid of the polychaete, Nereis virens, by density gradient centrifugation. The lipoprotein was present in both sexes and moved as a uniform band in an agarose gel. The average diameter of the lipoprotein particles determined by electron microscopy was 42 nm with a thickness of 10 nm. SDS electrophoresis showed two apoprotein subunits with molecular masses of 247 and 85 kDa, respectively. In lectin blots, both apoproteins were reactive with Concanavalin A indicating the presence of N-glycans. The small subunit was also reactive with peanut lectin, indicating additional O-glycosylation. The total lipid content was 48% and consisted mainly of phospholipids and some diglycerides as judged by thin layer chromatography. The estimated native molecular mass of N. virens lipoprotein (∼675 kDa) lies in the range of vertebrate high-density lipoprotein and insect lipophorins. The size of the apoproteins is similar to those found in insects, while the composition of the lipid fraction is more similar to that of crustacean lipoproteins.