Structure and evolution of ribosomes
1981
Wittmann, H.G. | Dijk, J.
Ribosomes are the only cell organelles occurring in all organisms. E. coli ribosomes which are the best characterized particles, consist of three RNAs and 53 different proteins. All components have been isolated and studied using chemical, physical and immunological methods. The primary structures of the RNAs and of almost all proteins are known. Information about the secondary structure of the proteins derives from circular dichroism measurements and from secondary structure prediction methods. The tertiary structure is being studied using limited proteolysis, proton magnetic resonance and in some cases crystallization and X-ray analysis. The following methods are being used to elucidate the architecture of the ribosomal particle: immune electron microscopy, neutron scattering; protein-protein, protein-RNA and RNA-RNA cross-linking; total reconstitution of ribosomal subunits. The combination of results, which are described in some detail, yields a relatively clear definition of the architecture of the ribosomal particle. Many mutants have been isolated in which one or a few ribosomal proteins are altered or deleted. The genetic and biochemical characterization of these mutants allows information about the structure, function and biosynthesis of ribosomes and their components. Ribosomal proteins from various prokaryotic and eukaryotic species have been compared using two-dimensional gel electrophoresis, immunological methods, reconstitution and amino acid sequence analysis. These studies show a rather strong homology among prokaryotes but only a weak homology between prokaryotic and eukaryotic ribosomal proteins. On the other hand, the sequences of the ribosomal RNAs are more conserved during evolution than the sequences of ribosomal proteins.
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