Ribosomes are ancient subcellular organelles that are responsible for translation of messenger RNA into protein. The structures of ribosomes from all living organisms are fundamentally related, indicating that all ribosomes use the same basic mechanisms in protein synthesis. A major question facing molecular biologists is to understand the molecular basis of translation, and how the ribosome works. There is increasing evidence that the ribosome is a dynamic molecular machine, with moving parts that are largely composed of RNA. It is possible that understanding translation at this level may contribute to knowledge of the origins of life, as well as shedding light on the question as to why RNA stands at the center of so many fundamental cellular processes. This project is based on the structural knowledge provided in recent years by x-ray crystal structures and cryo-EM reconstructions of ribosomes and ribosomal complexes. These structures are essential for an atomic level understanding of the mechanism of action of ribosomes, but are not in themselves sufficient. Structures suggest possible mechanisms, but are unable to prove their existence. Accordingly, molecular genetics approaches will be used to directly test models that have been proposed for several basic ribosomal mechanisms, particularly ones that implicate movement of parts of the ribosome structure. These studies will make use of recently implemented methodologies, including the use of "specialized ribosomes" and affinity-tagging of rRNA that make possible direct read-out of in vivo protein synthesis activity of mutant ribosomes, and isolation of pure populations of mutant ribosomes for in vitro studies. Dr. Noller has trained a large number of graduate and postdoctoral students, many of whom have gone on to independent positions and have developeed productive and successful research programs of their own. He has consistently made strains, mutants and clones developed in his laboratory available to othr researchers throughout the world. Both these elements of broader impact will continue as a result of this project.
