The in situ architecture of Escherichia coli ribosomal RNA derived by electron spectroscopic imaging and three-dimensional reconstruction.

The structures of the large and small ribosomal subunits of Escherichia coli were reconstructed using spectroscopic electron microscopy and quaternion-assisted angular reconstitution to resolutions of better than 4 nm. In addition, the distributions of phosphorus within these complexes were reconstructed. The three-dimensional reconstruction of the distribution of this atomic element is an extension of microanalysis (in two dimensions) for phosphorus identification and mapping, as a signature of the arrangement of the phosphate backbones of the constituent ribosomal RNAs. The results on both the phosphorus reconstructions and the total reconstructions (protein and ribosomal RNA) reveal several passageways through both subunits. The structures correspond favourably with other independent reconstructions of the whole E. coli ribosome from cryoelectron micrographs and their accompanying models of translation (Frank et al., Nature, 376, 441-444, 1995; Stark et al., Structure, 3, 815-821, 1995). The overall reconstructions in conjunction with the phosphorus (rRNA) distributions are the first to be achieved synchronously for this nucleoprotein complex.