Dark field EM of the RNA of the small subunit of the E. coli ribosome

Abstract

We have embarked on a series of EM experiments using the dark field mode in an attempt to ascertain how much of a role the ribonucleic acid (RNA) component of the ribosome has in determining the structure of the protein-nucleic acid complex. We have observed that treatment of specimens of the smaller subunit enhances the visibility of band-like structures on the "back" of the subunit. In total, though not necessarily all appearing at once on a single individual, three parallel bands of 20 Å diameter are seen (Fig. 2). We have speculated that these are double stranded sections of the RNA that emerge on the surface. This does not preclude external single stranded sections that are not as prominent, however. The identification of the bands with double stranded external RNA is still subject to further testing. In a very recent experiment we have examined a heated RNAase digestion product that has been shown to lack a section of its RNA.