ELECTRON-MICROSCOPIC STUDY OF FREE AND RIBOSOME BOUND RIBOSOMAL-RNAS FROM ESCHERICHIA-COLI

Abstract

The morphology of ribosomal subunits, nucleoprotein cores and free rRNA species from E. coli was studied by 2 high resolution EM techniques. Conventional transmission electron micrographs showed unfolding of 30S and 50S ribosomal subunits with increasing depletion of proteins. With dedicated (0.3 nm resolution) scanning transmission electron microscopy it was possible to visualize unstained freeze dried ribosomal subunits and free rRNA species without artifacts of staining and structural distortion by air drying. By this technique, the mass of individual ribosomal particles and rRNA molecules was also determined. While the ribosomal subunits displayed their characteristic structural features and mass, free rRNA species appeared unfolded and polydisperse. Distinct conformational differences apparently exist between free rRNA species and native ribosomal subunits of E. coli.