Abstract
Lipovitellin (LV) is essential in crustacean eggs for embryo viability and development. Two LV were isolated from eggs of Macrobrachium borellii. corresponding to early (LVe ) and late (LVl) embryo developing stages. They differ in lipid composition but not in lipid/protein ratio or apoprotein composition. Structural information was obtained by fluorescence spectroscopy, far-UV circular dichroism, partial trypsinolysis and electron microscopy applied to LVe and LVl and two partially delipidated forms of LVe generated by phospholipase A2 (LVp) or Triton X-100 (LVt) treatment. All LV forms contained two apoprotein subunits of 94 and 112 kDa, being the 112k Da subunit more accessible to trypsinolysis in all. Only in LVp, different cleavage sites appeared. Secondary structure was similar in LVe and LVl, but LVp and LVt showed a small increase in beta-sheet at expense of alpha-helix. Electron microscopy revealed a spheroidal morphology in all LV and a decreased size in LVp. Delipidated LVs were more resistant to denaturation with guanidinium-HCl. Acrylamide quenching of tryptophan fluorescence was more efficient in delipidated LVs, probably due to apolipoprotein rearrangement, as reinforced by fluorescence anisotropy. It is concluded that LV stability, shape, and apoprotein conformation is not largely affected by the changes in lipid composition that take place during embryogenesis.
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