Approaching translation at atomic resolution

Atomic resolution structures of 50S and 30S ribosomal particles have recent ly been solved by X-ray diffraction. These ribosomal structures show often unusual folds of ribosomal RNAs and proteins, and provide molecular explana tions for fundamental aspects of translation. In the 50S structure, the act ive site for peptide bond formation was localized and found to consist of R NA. The ribosome is thus a ribozyme. In the 30S structures. tRNA binding si tes were located. and molecular mechanisms for ribosomal fidelity were prop osed. The 30S subunit particle has three globular domains, and relative mov ements of these domains may be required for translocation of the ribosome d uring protein synthesis. The structures are consistent with and rationalize decades of biochemical analysis of translation and usher in a molecular ag e in understanding the ribosome.