Purification and biochemical characterization of a protein complex from the sea urchin, Strongylocentrotus purpuratus: Possible functional role for the yolk granule organelle during embryonic development

Several studies have demonstrated that sea urchin yolk granules harbor several components destined for export. Therefore, we hypothesized that the yolk granules might be involved in transportation and fusion events. We have isolated a protein of 240 kDa present in the yolk granules of eggs from the sea urchin, Strongylocentrotus purpuratus, by ion exchange chromatography using the anion exchange resin, Q-Sepharose Fast Flow. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of this protein under non-reducing conditions revealed that this was a complex composed of three polypeptides of 160 kDa, 120 kDa and 90 kDa. Western blots performed using the anti-toposome antibody demonstrated that the 240 kDa protein complex was the toposome which was proteolytically processed, while the 160 kDa polypeptide was the major yolk granule protein derived from it. Peptide mapping confirmed that the 240 kDa toposome was the precursor for the 160 kDa major yolk granule protein.; We have biochemically characterized the calcium-dependent phospholipid binding and vesicular aggregating activity of the 240 kDa protein complex. (Abstract shortened by UMI.)...