Steitz, Thomas Arthur (1940-2018), was an American biochemist. He shared the 2009 Nobel Prize in chemistry for his work with bacterial ribosomes. Ribosomes are the parts of a cell that assemble proteins (see Cell (Producing proteins) ). Steitz studied the structure and function of ribosomes using X-ray crystallography. In X-ray crystallography, scientists produce images of molecules by condensing them into crystals and bombarding them with X rays. Steitz shared the prize with two other ribosome researchers, the American biochemist Venkatraman Ramakrishnan and the Israeli crystallographer Ada Yonath.
A ribosome consists of two parts, called the large subunit and the small subunit. Both subunits consist of several large molecules bound together into a single structure. Steitz became the first to produce an image of the large subunit that revealed the individual atoms in the structure. To produce such an image, one major problem Steitz had to overcome concerned phase angle. Phase angle is a property of light—in this case, the X rays—that crystallographers must measure to produce a model of a molecule or structure that has depth—that is, a three-dimensional model. Traditional methods for finding the angles do not work with a structure as large as a ribosome. By combining several techniques, Steitz was able to determine the angles.
After revealing the structure of the large subunit, Steitz determined that the ribosome functions as a rare type of enzyme. Enzymes are molecules—almost always proteins—that speed up chemical reactions in living things. Steitz determined that the ribosome is not a protein enzyme, but a rare ribozyme. The portion of a ribozyme that speeds up the reaction is made not of protein but of RNA (ribonucleic acid). RNA is an important molecule in living things, but it is not usually associated with enzyme activity. Steitz’s work has important applications in antibiotic, medical, and pharmaceutical research.
Steitz was born on Aug. 23, 1940, in Milwaukee. He graduated from Lawrence College (now Lawrence University) in Appleton, Wisconsin, in 1962. In 1966, he received a Ph.D degree in biochemistry and molecular biology from Harvard University in Cambridge, Massachusetts. He remained at Harvard as a postdoctoral fellow for one year. In 1967, he accepted a postdoctoral position at the Medical Research Council Laboratory of Molecular Biology in Cambridge, England. In 1970, Steitz joined the faculty of Yale University in New Haven, Connecticut. He died on Oct. 9, 2018.
See also Ramakrishnan, Venkatraman ; Yonath, Ada E.
