Herschel K. Mitchell Chemistry

tothenic acid. He was the had to learn basic genetics, O b i t u a r i e s discoverer of folic acid and which he soon did. was primarily responsible for When Beadle left Stanford its initial isolation from four in 1946 to become chairman tons of spinach. of the Division of Biology at From Texas, Mitchell Caltech, he took Mitch with moved, in 1943, to Stanford him, along with other senior University as a research asso- members of his research ciate in the laboratory of group. In 1949, Mitchell George Beadle. The Beadle became associate professor lab was investigating the role of biology at Caltech, and of genes in metabolism— in 1953 full professor. He work that had been made retired in 1984 as professor possible by Beadle and emeritus. Tatum’s discovery of muta- Over the years, Mitch and H ERSCHEL K ENWORTHY M ITCHELL tions in the mold Neurospora the excellent students and 1913 — 2000 that blocked the synthesis of postdocs he attracted to his specific vitamins, amino laboratory made important acids, and nucleic acid bases. contributions to the develop- At the time, Neurospora was ing field of biochemical by Norman Horowitz, the only genetically well- genetics. Among the most Professor of Biology, understood microorganism. consequential of these was the Emeritus Its genetic organization and first demonstration of an metabolic properties made it enzyme missing from a ideal for the revolutionary Neurospora mutant. Such a program initiated by Beadle demonstration was one of the and Tatum that succeeded in early goals of the Beadle lab. Emeritus Professor of uniting genetics and bio- Up to that point, the evi- Biology Herschel K. Mitchell chemistry. Mitchell occupied dence had established that died on April 1, following a a unique position in the specific gene mutations cause stroke, his second in a period Beadle group. He was a blockage of specific biosyn- of 10 years. The first stroke genuine glassblowing chemist thetic reactions, and it was confined him to a wheelchair, with little knowledge of assumed that loss of the but he retained the ability to genetics, whereas the others enzyme catalyzing the reac- speak and was frequently seen were geneticists, largely self- tion was responsible. The on campus with his atten- trained in chemical proce- demonstration by Mitchell Herschel Mitchell in 1988, dant, Douglas Ross. dures. Mitch, for his part, and Lein that the enzyme photographed by his wife, Mitch, as he was known to Annamarie. his friends, played an important role in the advances that revolutionized the science of biology in the 20th century. Born on November 27, 1913, in Los Nietos, California, near Los Angeles, he attended Pomona College and gradu- ated in 1936 with honors in chemistry. This was followed in 1938 by a master’s degree in chemistry from Oregon State College and, in 1941, a PhD in chemistry from the University of Texas. At Oregon State, Mitchell worked with biochemists R. J. Williams and E. E. Snell, and he accompanied them when they moved to the University of Texas in 1940. In 1995 Mitchell attended Ed Lewis’s Nobel Prize celebration. From left: His most significant research biologists Norman Horowitz, Lewis, Seymour Benzer, Mitchell, Norman in those years dealt with the B vitamins folic and pan- Davidson, and Ray Owen, all professors emeriti. ENGINEERING & SCIENCE NO . 2 41 Faculty File Mitchell appeared in the January 1972 E&S with some of his Drosophila—in this case miniflies he had produced by injecting two- day-old larvae with a polypeptide derived from bee venom. M EYEROWITZ N EW C HAIR OF B IOLOGY (tryptophan synthetase in this problem of development in most others. This was the Elliot Meyerowitz, a spe- case) was absent from the higher organisms and turned first chemical work ever done cialist in the genetics of mutant but present in the his attention to the geneti- on heat-shock, and it gave flowering plants, has been wild type from which the cally important insect Dro- rise to a large amount of named chair of the Division mutant arose was an essential sophila. Development can be research on its mechanism of Biology at the California step in the argument that described, at one level, as the and biological role. It has Institute of Technology. eventually established that programmed synthesis of recently been found that the Meyerowitz replaces Mel genes control metabolism by specific proteins through proteins induced by heat- Simon, who is returning to producing (in a manner not time. Since the structure of shock are principally “chaper- full-time faculty and research then understood) the enzymes every protein of an organism ones” that function in the duties after serving five years required for specific chemical is encoded in the organism’s refolding of proteins damaged in the office. reactions, the rule being that genes, development involves by heat stress. The phenom- A member of the Caltech one gene governed the syn- the activation of specific enon is not restricted to Dro- faculty since he arrived as an thesis of one particular genes at the time and place sophila, but has been found in assistant professor in 1980, enzyme. Beadle called this the proteins they encode all species examined, from Meyerowiz has been professor the “one-gene-one-enzyme” become needed for produc- bacteria to man—indicating of biology since 1989 and was hypothesis. It later was re- tion of the organism. that it is very ancient and also executive officer from 1995 to fined to become “one-gene- The problem that came very important. Since 1973, 2000. His primary research one-protein” and, finally, to occupy Mitch’s attention the study of heat-shock has interest is the genes that con- since some proteins are com- starting in the 1970s and to become a new area of biologi- trol the formation of flowers, posed of more than a single which he made important cal research, one for which and how altering these genes polypeptide, each with its contributions was the phe- Mitchell was a founding will affect flower develop- own gene, “one-gene-one- nomenon of heat-shock. father. ■ ment. He has identified polypeptide.” Other refine- Heat-shock refers to the effect mutations that cause petal ments are now recognized, of brief exposure to heat on cells to develop into stamens but all are reducible to the the biochemistry of cells and instead, and another mutation idea of a simple relation tissues. It had been known that causes these same em- between genes and proteins. since the early ’60s that heat- bryonic petals to become Mitch’s interests were wide shock causes “puffing” of sepals (see E&S, 1997, No. 4). ranging. His published specific regions of the giant Meyerowitz earned his works include papers dealing salivary chromosomes of bachelor’s degree in biology, with the biosynthesis in Drosophila, and it had been summa cum laude, at Colum- neurospora of adenine, pyri- suggested that puffing was an bia University in 1973, and midine nucleosides, nicotinic indicator of gene activity. In his doctorate at Yale Univer- acid, lysine, histidine, and 1973 Mitchell, together with sity in 1977. He received the tryptophan; and they include Swiss biochemist Alfred Tis- John S. Nicholas Award for studies on topics as diverse as sières, began to work on heat- Outstanding Biology Disser- maternal inheritance and shock. They made the basic tation from Yale for his doc- temperature-sensitive mu- discovery that heat-shock toral reserach. He came to tants in this organism. induces the production of a Caltech following a post- In the early ’50s, Mitchell small number of proteins and doctoral appointment at became interested in the inhibits the production of Stanford. 42 ENGINEERING & SCIENCE NO . 2 .

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