The Nobel Prize has been awarded twice to scientists who worked on the discovery of the ribosome and its detailed structure. In 1974, George Emil Palade, a Romanian cell biologist, won the award in physiology and medicine for the discovery of ribosomes, the tiny granules that act as the cell’s protein factories. The 2009 Nobel Prize for chemistry went to Ada Yonath, Tom Steitz and Venkatraman Ramakrishnan for working out the structure of the ribosome.
Ada Yonath was born in Jerusalem in 1939. Her research into the structure of ribosomes began at Israel’s Weizmann Institute in the late 1970s, in collaboration with H.G. Wittmann of the Max Planck Institute in Berlin. Yonath applied a technique to crystallize ribosomes and study their three-dimensional structure. She credits her use of crystallization to a dream about bears packing away ribosomes before going into hibernation. While the initial crystal samples were fragile, Yonath and her team developed new techniques to freeze ribosome crystals at minus 185 degrees centigrade. This allowed X-rays to scan ribosomes without damaging them. In 2000 and 2001, her team published the first complete three-dimensional structures of bacterial ribosomes.
Born in India in 1952, “Venki” Ramakrishnan helped to uncover the structure of the smaller ribosome subunit, known as the 30S subunit, while working at the Laboratory of Molecular Biology in Cambridge, England. Ramakrishnan developed new methods that increased the accuracy of X-ray diffraction analysis. His new technique, known as “anomalous scattering,” involved introducing heavy atoms into ribosome crystals and applying X-rays specifically tuned to the introduced atoms. Crucial to his success was the ability to secure time in February 2000 -- via friendly connections -- on the Advanced Photon Source, an X-ray generating synchrotron that had recently been built at the Argonne Laboratory near Chicago.
Thomas A. Steitz
A Milwaukee native born in 1940, Thomas Steitz began working on ribosomal structure at the Yale Center for Structural Biology in 1995. In 2000, Steitz and his colleagues worked out the structure of the larger, 50S ribosome subunit using X-ray crystallography techniques. Steitz’s technique was to refine the work done by Yonath in which clusters of heavy atoms were introduced into frozen ribosome crystals and scanned for “phase” information -- the relationship between the ribosome structure and the X-ray’s wave pattern. Steitz’s group also used anomalous scattering, allowing them to uncover the 50S subunit's structure at about the same time that Yonath’s and Ramakrishnan's teams were announcing similar results.
Ribosomal RNA is transcribed from a cell's DNA. It then forms two subunits, a large and a small. Ribosomal RNA composes the bulk of a ribosome’s structure, while the remainder is made of large and small proteins. The subunits are separately transported throughout the cell body where they float freely in the cytoplasm. In eukaryotic cells, ribosomes also bind to the endoplasmic reticulum -- a cell organelle involved with protein synthesis and transport. The smaller subunit binds to messenger RNA that encodes genetic information. The larger subunit attaches to complexes made up of transfer RNA and an amino acid. During protein synthesis, the two ribosome subunits join together temporarily to translate messenger RNA into proteins with the help of various enzymes.