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J. Biol. Chem., Vol. 282, Issue 22, 17, June 1, 2007
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Covalent Bonds between Protein and DNA. Formation of Phosphotyrosine Linkage between Certain DNA Topoisomerases and DNA
(Tse, Y. C., Kirkegaard, K., and Wang, J. C. (1980) J. Biol. Chem. 255, 5560–5565)
Mapping the Active Site Tyrosine of Escherichia coli DNA Gyrase
(Horowitz, D. S., and Wang, J. C. (1987) J. Biol. Chem. 262, 5339–5344)
James Chuo Wang was born in Jiansu, China in 1936. Less than a year later, the Sino-Japanese War began. Wang lost his mother during the conflict, and his father remarried, moving the family to Taiwan in 1949 after the war. As a child, Wang wanted to study medicine but his father encouraged him to become an engineer. Because he was interested in chemistry, he decided to pursue chemical engineering. Wang earned a B.S. in 1959 from National Taiwan University and then served as an Assistant Instructor at the university until 1960. He then came to the United States to continue his studies in chemistry and earned a masters degree from the University of South Dakota in 1961 and a doctorate from the University of Missouri in 1964.
After receiving his degree, Wang became a research fellow at the California Institute of Technology and remained there until 1966 when he joined the faculty at the University of California. While at Berkeley, Wang was studying negative supercoiling of DNA when he noticed that one of his cell preparations lacked negative supercoiling. After several months of doing chromatography, he was able to isolate the enzyme that could remove supercoiling (1). He named this protein 
.
Wang recalls, "The manuscript was held up for quite some time as the journal's reviewers took their time to `believe' the results. I can imagine their bewilderment with this strange report of an unprecedented enzyme by someone with no track record in enzymology. For one whole year, I would wonder whether one day the whole thing would turn out to be an artifact. After one year, however, I myself was fully convinced. It probably took many others a few more years to accept the findings" (2).
In 1976, a second DNA topoisomerase was discovered in Escherichia coli (3). This enzyme, termed DNA gyrase or bacterial DNA topoisomerase II, was both a DNA topoisomerase and a DNA-dependent ATPase. The enzyme could negatively supercoil closed circular DNA in the presence of ATP and relax negatively supercoiled DNA slowly in the absence of ATP. Eventually, the topoisomerases were divided into two groups: type I topoisomerases and type II topoisomerases. Enzymes that fell into the type I category function by nicking one of the strands of the DNA double helix, twisting it around the other strand, and re-ligating the nicked strand. Type II topoisomerases make a double-stranded break in the DNA, pass another duplex DNA through this gap, and then reseal the break.
In 1977 Wang left Berkeley to join the faculty at Harvard University. He continued to work on topoisomerases, examining their properties and structure. "As enzymes, the DNA topoisomerases are magicians among magicians; they open and close gates in DNA without leaving a trace, and they enable two DNA strands or duplexes to pass each other as if the physical laws of spatial exclusion do not exist," Wang explained in his 1991 Journal of Biological Chemistry (JBC) Minireview on topoisomerases (4).
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In the second JBC Classic, Wang and David S. Horowitz look at the active site of E. coli DNA gyrase to determine which residues are involved in DNA binding. To do this, they specifically labeled the gyrase active site with 32P by cleaving 32P-labeled DNA with gyrase in the presence of oxolinic acid and digesting the resulting covalent complex of gyrase and DNA with a nuclease. The mixture was then proteolyzed and run on a gel, and the position of the labeled peptide in the primary sequence of gyrase was determined by sequencing the corresponding unlabeled peptide. Using this method, they found that tyrosine 122 of the A subunit of E. coli DNA gyrase is the tyrosine that becomes covalently bound to DNA when the enzyme breaks the phosphodiester bonds of DNA.
Wang remained at Harvard as the Mallinckrodt Professor of Biochemistry and Molecular Biology until his retirement in 2006. In recognition of contributions to academia, Wang is the holder of many titles and recipient of numerous awards. These include the National Academy of Sciences Award in Molecular Biology (1983), the Distinguished Alumnus Award form the University of Missouri School of Arts and Sciences (1991), the Distinguished Lecturer Award from Lehigh University (1991), and the Most Distinguished Chinese Scholar Lectureship from the Hong Kong Society of Scholars (1991). He was elected a member of Academia Sinica, Taipei, in 1982, a Fellow of the American Academy of Arts and Sciences in 1984, a member of the National Academy of Sciences in 1986, and an associate member of the Third World Academy of Sciences in the same year. Wang has served on the editorial boards of several journals, including the Journal of Molecular Biology, the Annual Review of Biochemistry, and Nucleic Acids Research.1
Wang's co-authors on these Classic papers have also gone on to have productive research careers. Yuk-Ching Tse-Dinh is now a professor at New York Medical College and a member of the JBC editorial board. Karla Kirkegaard is currently at the Stanford University School of Medicine where she is Professor and Chair of Microbiology and Immunology. Kirkegaard has received several awards and honors, including the Searle Scholar Award, a David and Lucile Packard Fellowship, an American Cancer Society Junior Faculty Award, an Ellison Foundation Senior Scholar Award in Global Infectious Disease, an appointment to the Howard Hughes Medical Institute, and the NIH Director's Pioneer Award. David S. Horowitz is currently an Assistant Professor in the Department of Biochemistry and Molecular Biology at the Uniformed Services University of the Health Sciences.
FOOTNOTES
1 Biographical information on James C. Wang was taken from Ref. 2. 
REFERENCES
. J. Mol. Biol. 55, 523–526[CrossRef][Medline]
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