Three-dimensional reconstruction and averaging of 50 S ribosomal subunits of Escherichia coli from electron micrographs.

Abstract Several individual 50 S ribosomal subunits of Escherichia coli (L7 and L12 split off) were reconstructed three-dimensionally from the electron micrographs of a tilting series. Four particles in “kidney” orientation were aligned by three-dimensional correlation methods and subsequently averaged. The averaged structure as well as the individual reconstructions show a stained, channel-like substructure inside the particle, which is tentatively explained by the hypothesis of positively stained RNA.