THE STRUCTURES OF INSECT LIPOPROTEINS

The insect hemolymph lipoprotein, lipophorin, exists as one of several distinct subspecies, whose lipid contents are correlated with physiological lipid transport needs. It has been shown that lipophorin subspecies are interconvertable, through the acquisition or loss of lipid from pre-existing subspecies. A hemolymph lipid transfer particle has been isolated and shown to function in facilitated lipid redistribution, giving rise to different subspecies. In the adult life stage, flight activity induces a dramatic enrichment of lipophorin with neutral glycerolipid as well as the exchangeable apolipoprotein, apolipophorin III. Apolipophorin III exists as an elongated bundle of five helices that is proposed to undergo a major conformational change upon lipoprotein binding whereby it exposes its hydrophobic interior which interacts with the lipid surface.