HnRNP particles from Drosophila melanogaster cells.

The isolation and characterization of HnRNP from cultured Drosophila melanogaster cells is described. HnRNP particles were extracted from the purified nuclei of sonication in the presence of rat liver cytosol RNAse inhibitor. The nuclear extract was centrifuged on a 15-30% sucrose gradient. The main part of the heterogeneous HnRNP material was localized in the 30 to 80S region of the sucrose gradient. According to the results of re-sedimentation studies the monomer particle was 45S. The buoyant density of HnRNP particles from different regions of the sucrose gradient were equal to approximately 1.4. The protein composition of the particles was analyzed by urea-SDS-polyacrylamide gel electrophoresis. There are five main and a few minor bands. Only the main polypeptides have a slightly higher molecular weight than those of the major polypeptides of 30S subparticles from rat liver nuclei. According to electron = microscopic studies the particles are heterogeneous and the average diameter was found to be 24-26 nm both on the basis of negative contrast and platinum-palladium shadowed pictures.