Dr. Susan Wang
Research & Interests
The “radical SAM (S-adenosyl-L-methionine)” enzyme superfamily was initially described in 2001. The members of this superfamily, numbering in the thousands, catalyze a wide variety of reactions, most of which have not been characterized. The few radical SAM enzymes that have been studied share only two obvious characteristics. 1 - They each contain an unusual iron-sulfur ([4Fe-4S]) cluster in which three ligands to the cluster are cysteine residues from the protein, while the fourth ligand is SAM. These cysteine residues are found in a CXXXCXXC amino acid motif considered to be the hallmark of this superfamily. 2 - They utilize a 5'-deoxyadenosyl (Ado-CH2•) radical generated from the homolytic cleavage of SAM to abstract a hydrogen atom from the appropriate substrate. Our lab is interested in the fundamental mechanistic issues surrounding the subfamily of radical SAM enzymes believed to catalyze interesting and difficult methyl transfer reactions required by some organisms for antibiotic biosynthesis. Little is understood about these enzymes, but like many other methyltransferases, they reportedly require methylcobalamin (a derivative of vitamin B12) for activity. Since either SAM or methylcobalamin can function as a methyl transfer agent, we wish to determine whether these proteins require one or both as cofactors (or perhaps substrates) in catalysis. We combine a variety of techniques spanning molecular biology, organic synthesis, nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopies, and protein chemistry. These studies will provide further insight into the biological pathways used for antibiotic synthesis, thus facilitating the design of new antibiotic compounds and leading to the improvement of industrial processes used for large-scale antibiotic production.
Wang, S. C. and Frey, P. A., “Binding Energy in the One-electron Reductive Cleavage of S-adenosylmethionine in Lysine 2,3-aminomutase, a Radical SAM Enzyme,” Biochemistry, 13;46(45):12889-95. (2007)
Wang, S. C., Johnson, W. H., Jr., Czerwinski, R. M., Stamps, S. L., and Whitman, C. P., “Kinetic and Stereochemical Analysis of YwhB, a 4-Oxalocrotonate Tautomerase Homologue in Bacillus subtilis: Mechanistic Implications for the YwhB- and 4-Oxalocrotonate Tautomerase-catalyzed Reactions,” Biochemistry, in press.
Wang, S. C., and Frey, P. A., “S-Adenosylmethionine as an Oxidant: the Radical SAM Superfamily,” Trends in Biochemical Sciences, 32, 101 (2007).
Golubkov, P.A., Johnson, W. H., Jr., Czerwinski, R. M., Person, M. D., Wang, S. C., Whitman, C. P., and Hackert, M. L., “Inactivation of the Phenylpyruvate Tautomerase Activity of Macrophage Migration Inhibitory Factor by 2-Oxo-4-phenyl-3-butynoate,” Bioorganic Chemistry, 34, 183 (2006).
Goodman, J. L., Wang, S. C., Alam, S., Ruzicka, F. J., Frey, P. A., and Wedekind, J. E., “The Structure and Mechanism of Ornithine Cyclodeaminase from Pseudomonas putida and Implications for the µ-Crystallin Family,” Biochemistry, 43, 13883 (2004).
Johnson W. H., Jr.,Wang, S. C., et al., “4-Oxalocrotonate Tautomerase, Its Homologue YwhB, and Active Vinylpyruvate Hydratase: Synthesis and Evaluation of 2-Fluoro Substrate Analogs,” Biochemistry, 43, 10490 (2004).
Alam, S., Wang, S. C., Ruzicka, F. J., Frey, P. A., and Wedekind, J. E., “Crystallization and X-ray Diffraction Analysis of Ornithine Cyclodeaminase from Pseudomonas putida,” Acta Crystallographica D: Biological Crystallography, 60, 941 (2004).
Azurmendi, H. F., Wang, S. C., Massiah, M. A., Poelarends, G. J., Whitman, C. P., and Mildvan, A. S., “The Roles of Active-Site Residues in the Catalytic Mechanism of trans-3-Chloroacrylic Acid Dehalogenase: A Kinetic, NMR, and Mutational Analysis,” Biochemistry, 43, 4082 (2004).
Wang, S. C., Johnson, W. H., Jr., Czerwinski, R. M., and Whitman, C. P., “Reactions of 4-Oxalocrotonate Tautomerase and YwhB with 3-Halopropiolates: Analysis and Implications,” Biochemistry, 43, 748 (2004).
Wang, S. C., Johnson, W. H., Jr., and Whitman, C. P., “The 4-Oxalocrotonate Tautomerase- and YwhB-catalyzed Hydration of 3E-Haloacrylates: Implications for the Evolution of New Enzymatic Activities,” Journal of the American Chemical Society, 125, 14282 (2003).
Wang, S. C., Person, M. D., Johnson, W. H., Jr., and Whitman, C. P., “Reactions of trans-3-Chloroacrylic Acid Dehalogenase with Acetylene Substrates: Consequences of and Evidence for a Hydration Reaction,” Biochemistry, 42, 8762 (2003).
Shine, N. R., Wang, S. C., Konopka, K., Burks, E. A., Duzgunes, N., and Whitman, C. P., “Secretory Leukocyte Protease Inhibitor: Inhibition of Human Immunodeficiency Virus-1 Infection of Monocytic THP-1 Cells by a Newly Cloned Protein,” Bioorganic Chemistry, 30, 249 (2002).
Almrud, J. J., Kern, A. D., Wang, S. C., et al., “The Crystal Structure of YdcE, a 4-Oxalocrotonate Tautomerase Homologue from Escherichia coli, Confirms the Structural Basis for Oligomer Diversity,” Biochemistry, 41, 12010 (2002).
Stamps, S. L., Taylor, A. B., Wang, S. C., Hackert, M. L., and Whitman, C. P., “Mechanism of the Phenylpyruvate Tautomerase Activity of Macrophage Migration Inhibitory Factor: Properties of the P1G, P1A, Y95F, and N97A Mutants,” Biochemistry, 39, 9671 (2000).