Topographical mapping of ribosomal RNAs in situ by electron spectroscopic imaging

Abstract

Visualization of the in situ location of the individual components of any macromolecular system is important for understanding its assembly, interactions, and function. Ribosomes, which are small cellular organelles involved in protein synthesis are high molecular weight nucleoprotein complexes composed only of proteins and RNAs. This “simple” composition of ribosomes enables us topographical studies directed either towards localization of the individual ribosomal protein and RNA molecules or merely to the determination of the distribution of the protein and RNA moieties within the ribosome and its subunits. We have utilized the recent progress in the development of microanalytical electron spectroscopic techniques, electron energy loss spectroscopy (EELS) in particular, and the unique distribution of the phosphorus atoms on the ribosome (the phosphorus atoms are present only in the structural backbone of the rRNA) for the direct tracing of the RNA molecules in situ.