Structural studies on the protein synthesis machinery

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In all living cells, protein synthesis is carried out in cellular organelles called ribosomes. These large ribonucleoprotein complexes are generally organized in two subunits of unequal size. In prokaryotic Escherichia coli ribosomes, the large (50S) subunit consists of 34 proteins and 5S and 23S rRNAs, while the small (30S) subunit is a complex of 21 proteins and 16S rRNA.All these proteins have been localized in the ribosome by immunoelectron microscopy and neutron scattering. In this project, we analyzed structures of three ribosomal proteins in the peptidyl transferase center of the ribosome. They are L2, L5 and L13. The protein L2 is known to be most important constituent of the peptidyl transferase center. That is, affinity-labeling studies have localized the protein L2 at or near the peptidyl transferase center of the 50S ribosomal subunit. L5 is one of the 5S rRNA binding protein and L13 is 23S rRNA binding protein. These structure analyses have demonstrated that ribosomal proteins represent unique targets for structural study. They provide new insights into protein evolution as well as protein-synthesizing machinery.