Michael F. Dunn
Professor of Biochemistry
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Physical Biochemistry Molecular Endocrinology
Ph.D., Georgia Institute of Technology, 1966
951-827-4235 |
Research in my laboratory involves studies in two areas: (1) the investigation of catalytic mechanisms of pyridoxalphosphate-requiring enzymes and other oligomeric enzymes; and (2) investigation of structure-function interrelationships for insulin and other protein hormones.
The primary objective of my research is to combine the results of our physical-chemical solution studies for these oligomeric enzymes and protein hormones with structural information from other laboratories to achieve a detailed understanding of the relationship between structure and function. My studies emphasize the use of rapid kinetic methods (i.e., stopped-flow rapid-mixing, and rapid scanning spectrophotometry) and other physical biochemical techniques (FT NMR, fluorescence, microspectrophotometry) to investigate chemical intermediates in catalysis and to investigate the interrelationship between subunit structure, function and regulation of biological activity.
We are currently investigating two allosteric systems, the tryptophan synthases from enteric bacteria and the zinc insulin hexamer. The allosteric effects in tryptophan synthase exert control over the catalytic processes at the alpha- and beta-sites of the bienzyme complex in such a way that the chemical transformations are coupled. In the insulin system, the allosteric effects mediate a conformational change that causes some residues to move by as much as 25Å, and this conformational transition forces the zinc sites to undergo a change in coordination geometry from octahedral to tetrahedral. Our work is directed toward the elucidation of the underlying mechanisms of these allosteric interactions.
SELECTED PUBLICATIONS
Dunn, M. F., Aguilar, V., Brzovic, P., Drewe, W. F., Houben, K. F., Leja, C. and Roy, M. The tryptophan synthase bienzyme complex transfers indole between the a- and b-sites via a 25-30 Å-long tunnel. Biochemistry 29, 8598-8607 (1990).
Brzovic , P.S., Sawa, Y., Miles, E.W. and Dunn, M.F. Evidence that mutations in a loop region of the a-subunit inhibit the transition from an open to a closed conformation in the tryptophan synthase bienzyme complex. J. Biol. Chem. 267, 13028-13038 (1992).
Hur, O., Leja, C., & Dunn, M. F. Evidence of a low-barrier hydrogen bond in the tryptophan synthase catalytic mechanism. Biochemistry 35, 7378-7386 (1996).
Pan, P., Woehl, E., and Dunn, M. F. Protein architecture, dynamics, and allostery in tryptophan synthase channeling. Trends in Biochemical Sciences 22, 22-27 (1997).
Rahuel-Clermont, S., French, C. A., Kaarsholm, N. C., & Dunn, M. F. Mechanisms of stabilization of the insulin hexamer through allosteric ligand interactions. Biochemistry 36, 5837-5845 (1997).
Bloom, C. R., Heymann, R., Kaarsholm, N. C., & Dunn, M. F. Binding of 2,6- and 2,7-dihydroxynaphthalene to wild-type and E-B13Q insulins: Dynamic, equilibrium and molecular modeling investigations. Biochemistry 36,12746-12758 (1997).
Bloom, C. R., Kaarsholm, N. C., Ha, J. & Dunn, M. F. Half-site reaactivity, negative cooperativity, and positive cooperativity: Quantitative considerations of a plausable model. Biochemistry 36, 12759-12765 (1997).
Woehl, E. & Dunn, M. F. Mechanisms of monovalent cation action in enzyme catalysis: The first stage of the tryptophan synthase b-reaction. Biochemistry 38, 7118-7130 (1999).
Woehl & Dunn, M. F. Mechanisms of monovalent cation action in enzyme catalysis: The tryptophan synthase a-, b- and ab-reactions. Biochemistry 38, 7131-7141 (1999).
Mozzarelli, A., Peracchi, A., Rovegno, B., Dale, G., Rossi, G. L. & Dunn, M. F. Effect of pH and Monovalent Cations on the Formation of Qunionoid Intermediates of the Tryptophan Synthase a 2 b 2 Complex in Solution and in the Crystal. J. Biol. Chem. 275, 6956-6962 (2000).
Schlein, M., Havelund, S., Kristensen, C., Dunn, M., F., and Kaarsholm, N. C. Ligand-Induced Conformational Change in the Minimized Insulin Receptor. J. Mol. Biol. 303, 161-169 (2000).
Weber-Ban, E., Hur, O., Bagwell, C., Banik, U., Yang, L.-H., Miles, E. E., and Dunn, M. F. Investigation of Allosteric Linkages in the Regulation of Tryptophan Synthase: The Roles of Salt Bridges and Monovalent Cations Probed by Site-Directed Mutation, Optical Spectroscopy, and Kinetics. Biochemistry 40 , 3497-3511 (2001).
Ferrari, D., Diers, J. R., Bocian, D, F., Kaarsholm, N. C., and Dunn, M. F. Raman Signatures of Ligand Binding and Allosteric Conformation Change in the Insulin Hexamer. Biopolymers: Biospectroscopy 58, 249-260 (2001).
Ferrari, D., Yang, L.-H., Miles, E. W., and Dunn, M. F. The b D305A Mutant of Tryptophan Synthase Shows Strogly Perturbed Allosteric Regulation and Substrate Specificity. Biochemistry 40 , 7421-7432 (2001).
Jhee, K.-H., Niks, D., McPhie, P., Dunn, M. F., and Miles, E. W. The Reaction of Yeast Cystathionine b -Synthase is Rate-Limited by the Conversion of Aminoacrylate to Cystathionine. Biochemistry 40 , 10873-10880 (2001).
Jhee, K.-H., Niks, D., McPhie, P., Dunn, M. F., and Miles, E. W. Yeast Cystathionine b -synthase Reacts with L-Homocysteine to Form a New Amino Acid, 3-Methyl-L- cystathionine. Biochemistry 41 , 1828-1835 (2002).
Harris, R. M. and Dunn, M. F. Intermediate Trapping via a Conformational Switch in the Na + Activated Tryptophan Synthase Bienzyme Complex . Biochemistry 41 , 9982-9990 (2002).
Hur, O., Niks, D., Casino, P. and Dunn, M. F. Proton Transfers in the b -Reaction Catalyzed by Tryptophan Synthase. Biochemistry 41 , 9991-10001 (2002).
Kulik, V., Weyand, M., Seidel, R. Niks, D., Arac, D., Dunn, M. F., and Schlickting I. On the role of a Thr 183 in the allosteric regulation and catalytic mechanism of tryptophan synthase. J. Mol. Biol. 324, 677-690 (2002).
Schlein, M., Ludvigsen, S., Olsen, H. B., Dunn, M. F., and Kaarsholm, N. C. Spectroscopic characterization of insulin and small molecule ligand binding to the insulin receptor. Spectroscopy 16 , 147-159 (2002).
Huffman, H. A., Sadeghi, M., Seemuller,E., Baumeister, W., and Dunn, M. F. Proteasome - Cytochrome c Interactions: A Model System for Investigation of Proteasome Host-Guest Interactions. Biochemistry 42 , 8679-8686 (2003).
Ferrari, D., Niks, D., Yang, L.-H., Miles, E. W., & Dunn, M. F. Allosteric Communication in the Tryptophan Synthase Bienzyme Complex: Roles of the b -Subunit Aspartate 305-Arginine 141 Salt Bridge . Biochemistry 42 , 7807-7818 (2003).
Olsen, H. B., Leuenberger-Fisher, M. R., Kadima, W., Borchardt, D., Kaarsholm, N. C., & Dunn, M. F. Structural Signatures of the Complex Formed Between 3-Nitro-4-hydroxybenzoate and the Zn(II)-Substituted R 6 Insulin Hexamer. Protein Science, 1902-1913 (2003).
Bonaccio, M., Ghaderi, N., Borchardt, D., and Dunn, M. F. Insulin Allosteric Behavior: Detection, Identification and Quantification of Allosteric States via 19-F NMR. Biochemistry, 44 , 7656 -7668 (2005).
Dunn, M. F. Zinc-ligand Interactions Modulate Assembly and Stability of the Insulin Hexamer - A Review. Biometals, in press (2005).
Kulik, V., Hartmann, E., Weyand, M., Frey, M., Gierl, A., Niks, N., Dunn, M. F., Schlichting, I., On the Structural Basis of the Catalytic Mechanism and the Regulation of the alpha Subunit of Tryptophan Synthase from Salmonella typhimurium and BX1 from Maize, Two Evolutionarily Related Enzymes J. Mol. Biol. , In Press (2005).