Advertisement

Unraveling the Enzymology of Oxidative Phosphorylation: the Work of Efraim Racker

Open AccessPublished:January 27, 2006DOI:https://doi.org/10.1016/S0021-9258(20)70795-7
      Partial Resolution of the Enzymes Catalyzing Oxidative Phosphorylation. I. Purification and Properties of Soluble, Dinitrophenol-stimulated Adenosine Triphosphatase (Pullman, M. E., Penefsky, H. S., Datta, A., and Racker, E. (1960) J. Biol. Chem. 235, 3322–3329)
      Partial Resolution of the Enzymes Catalyzing Oxidative Phosphorylation. II. Participation of a Soluble Adenosine Triphosphatase in Oxidative Phosphorylation (Penefsky, H. S., Pullman, M. E., Datta, A., and Racker, E. (1960) J. Biol. Chem. 235, 3330–3336)
      Efraim Racker (1913–1991) was born in the town of Neu Sandez, Poland. At the age of 2, he and his parents moved to Vienna, where Racker grew up. After finishing high school, he went to the University of Vienna to study medicine. Because his graduation from medical school in 1938 was around the time Hitler marched into Austria, Racker decided to leave while it was still possible and fled to Great Britain where J. Hirsh Quastel offered him a job at Cardiff City Mental Hospital in Wales. There, Racker tried to find biochemical causes for mental diseases. When Great Britain entered the war, Racker lost his job at Cardiff and was interned on the Isle of Man where he practiced medicine for the first time in his life. Although he enjoyed being a doctor, he decided to try his luck as a researcher in the United States.
      His first appointment was as a research associate in physiology at the University of Minnesota, Minneapolis, from 1941 to 1942. There, Racker carried on his search for a biochemical basis for brain diseases and showed that polio virus inhibited glycolysis in the mouse brain. Despite spending a year doing research, Racker once again found himself working as a physician when he accepted a position at the Harlem Hospital in New York City. His career in biochemistry began in earnest in 1944 when he was appointed assistant professor of microbiology at the New York University Medical School. During his time in New York, Racker continued his glycolysis studies and found that the inhibition could be overcome by the addition of glutathione. This led to his discovery that glyoxylase converts glyoxal to glycolic acid via a carboxyl-S-glutathione intermediate (
      • Racker E.
      The mechanism of action of glyoxalase..
      ). This was the first “energy-rich” thioester of biological relevance to be identified. Similarly, Racker and his technician Isidore Krimsky showed that glyceraldehyde 3-phosphate oxidation occurred through a thiol ester enzyme intermediate (
      • Racker E.
      • Krimsky I.
      The mechanism of oxidation of aldehydes by glyceraldehyde-3-phosphate dehydrogenase..
      ).
      In 1952, Racker was offered the position of associate professor at Yale Medical School, which he accepted. There, he continued to work on carbohydrate metabolism and discovered and purified trans-ketolase, a key enzyme in the pentose phosphate pathway. His stay in New Haven lasted 2 years and then he accepted the position of chief of the Nutrition and Physiology Department at the Public Health Research Institute of the City of New York. At first, Racker continued to work on the mechanism of glycolysis and the pentose phosphate pathway but then turned to the regulation of glycolysis. He showed that glycolysis was dependent on the continuous regeneration of ADP and inorganic phosphate by ATPase.
      Soon after Racker moved to the Public Health Research Institute, Maynard E. Pullman joined his department. Pullman had just earned a Ph.D. from Johns Hopkins University (1953) and spent a year as a fellow in pediatrics. Upon his arrival at the Public Health Research Institute he decided he wanted to determine the mechanism of ATP synthesis in mitochondria and chloroplasts. At that time, it was assumed that ATP synthesis was coupled to respiration through a “high energy” intermediate. Pullman and Racker, joined by Anima Datta and graduate student Harvey S. Penefsky, started by attempting to isolate the enzymes involved in ATP synthesis. They obtained fresh bovine hearts and, using a mechanical blender, isolated several grams of mitochondrial membrane fragments, which catalyzed oxidative phosphorylation. These submitochondrial particles were then vigorously shaken with tiny glass beads in a shaker built by Peter M. Nossal. The shaker was considered so dangerous that Nossal screwed it to the floor of a separate room, operated it by remote control, and allowed nobody else to touch it. When the mitochondrial fragments were sedimented in an ultracentrifuge, they still respired but no longer synthesized ATP. However, Racker and his co-workers discovered that oxidative phosphorylation could be restored if the supernatant was added back to the fragments.
      While attempting to isolate the soluble component that made oxidative phosphorylation possible, Racker and co-workers discovered that an ATPase was purified together with the phosphorylation activity. The purification and properties of this ATPase are the subjects of the first Journal of Biological Chemistry (JBC) Classic reprinted here. Eventually, the researchers realized that this ATPase was in fact the coupling factor that restored oxidative phosphorylation. They named this first enzyme of oxidative phosphorylation Factor 1 or F1. The second JBC Classic reprinted here provides the evidence that the coupling and ATPase activity are both catalyzed by F1.
      After the publication of these papers, Pullman remained at the Public Health Research Institute and was eventually promoted to associate director in 1983. He then left the Institute to become a senior research scientist at Columbia University's College of Physicians and Surgeons in 1989 where he remained until 1992.
      Racker continued to work on ATP synthesis and together with Vida Vambutas he purified a similar coupling factor from spinach chloroplasts (
      • Vambutas V.K.
      • Racker E
      Partial resolution of the enzymes catalyzing photophosphorylation. I. Stimulation of photophosphorylation by a preparation of a latent, Ca2+-dependent adenosine triphosphatase from chloroplasts..
      ). Later, with Yasuo Kagawa, Racker subfractionated submitochondrial particles with cholate and salt and identified a membrane factor that anchored F1 to the membrane and rendered it cold-stable and sensitive to the toxic antibiotic oligomycin (
      • Kagawa Y.
      • Racker E.
      Partial resolution of the enzymes catalyzing oxidative phosphorylation. IX. Reconstruction of oligomycin-sensitive adenosine triphosphatase..
      ). They named this insoluble F1-binding factor Fo, with the subscript signifying the letter “o” for oligomycin and not zero, as is often thought.
      In 1966, Racker left the Public Health Research Institute to help create and lead the biochemistry department of a new biology unit at Cornell University. By this time, Racker was convinced that oxidative phosphorylation was not mediated by a high energy chemical intermediate but by a transmembrane proton gradient as proposed by Peter Mitchell (
      • Mitchell P.
      Coupling of phosphorylation to electron and hydrogen transfer by a chemiosmotic type of mechanism..
      ). Joined by Walther Stoeckenius, Racker incorporated bacteriorhodopsin, a protein that functioned as a light-driven proton pump, and the F1Fo-ATPase into liposomes (
      • Racker E.
      • Stoeckenius W.
      Reconstitution of purple membrane vesicles catalyzing light-driven proton uptake and adenosine triphosphate formation..
      ). They showed that the protons pumped out by the illuminated bacteriorhodopsin flowed back through the F1Fo-ATPase and generated ATP from ADP and inorganic phosphate, proving that Mitchell's hypothesis was correct.
      In the years that followed, Racker and his colleagues reconstituted a variety of different membrane enzymes into liposomes and established reconstitution as a powerful approach for determining the mechanics of pumps, transporters, and receptors. As a result of his work, numerous prestigious honors and prizes were awarded to Racker, such as the Warren Triennial Prize in 1974, the National Medal of Science in 1976, the Gairdner Award in 1980, and the American Society of Biological Chemistry's Sober Memorial Lectureship. He was elected to the American Academy of Arts and Sciences and the National Academy of Sciences and was an Associate Editor for the JBC as well as a member of the JBC editorial board. Racker also came up with the maxim “Don't waste clean thinking on dirty enzymes,” which is one of the Ten Commandments of Enzymology (
      • Kornberg A.
      Ten commandments: lessons from the enzymology of DNA replication..
      ).
      All biographical information on Efraim Racker was taken from Ref.
      • Schatz G.
      .
      1All biographical information on Efraim Racker was taken from Ref.
      • Schatz G.
      .

      References

        • Racker E.
        The mechanism of action of glyoxalase..
        J. Biol. Chem. 1951; 190: 685-696
        • Racker E.
        • Krimsky I.
        The mechanism of oxidation of aldehydes by glyceraldehyde-3-phosphate dehydrogenase..
        J. Biol. Chem. 1952; 198: 731-743
        • Vambutas V.K.
        • Racker E
        Partial resolution of the enzymes catalyzing photophosphorylation. I. Stimulation of photophosphorylation by a preparation of a latent, Ca2+-dependent adenosine triphosphatase from chloroplasts..
        J. Biol. Chem. 1965; 240: 2660-2667
        • Kagawa Y.
        • Racker E.
        Partial resolution of the enzymes catalyzing oxidative phosphorylation. IX. Reconstruction of oligomycin-sensitive adenosine triphosphatase..
        J. Biol. Chem. 1966; 241: 2467-2474
        • Mitchell P.
        Coupling of phosphorylation to electron and hydrogen transfer by a chemiosmotic type of mechanism..
        Nature. 1961; 191: 144-148
        • Racker E.
        • Stoeckenius W.
        Reconstitution of purple membrane vesicles catalyzing light-driven proton uptake and adenosine triphosphate formation..
        J. Biol. Chem. 1974; 249: 662-663
        • Kornberg A.
        Ten commandments: lessons from the enzymology of DNA replication..
        J. Bacteriol. 2000; 182: 3613-3618
        • Schatz G.
        Biographical Memoir of Efraim Racker. 70. National Academy of Sciences, Washington, D. C.1996: 320-346