Our current research interests focus on studies of the mechanisms of enzymes that use folic acid as a cofactor. We have emphasized the studies of three enzymes: methylenetetrahydrofolate reductase, cobalamin-dependent methionine synthase and cobalamin-independent methionine synthase. Methylenetetrahydrofolate reductase is a flavoprotein that regulates a key branch point in folate metabolism and regulates the supply of one carbon units that are used to methylaate homocysteine to form methionine. Recently, a frequent mutation in this enzyme has been shown to be associated with risk for neural tube defect and for the development of cardiovascular disease in humans. We first studied the biochemical effects of a mutation homologous to this mutation in methylenetetrahydrofolate reductase from E. coli, and have shown that this mutation leads to enhanced loss of the flavin cofactor and dissociation of the tetrameric enzyme into dimers. In collaboration with Dr. Martha Ludwig and Brian Guenther, the structure of the wild-type bacterial enzyme was determined. More recently, Dr. Kazuhiro Yamada in my laboratory has expressed and purified human methylenetetrahydrofolate reductase, and has shown that the mutation leads to very similar changes in the properties of the human enzyme.
We are also interested in the catalytic mechanisms of cobalamin-dependent and cobalamin-independent methionine synthase:two completely unrelated enzymes that catalyze almost identical chemical reactions. We want to know whether the strategies for catalysis are similar or different. Does nature have more than one way to skin a cat? Our preliminary results suggest that the strategies for catalysis are strikingly similar.
Evans, J. C., Huddler, D. P., Hilgers, M. T., Romanchuk, G., Matthews, R. G., and Ludwig, M. L. (2004) Structures of the N-terminal modules imply large domain motions during catalysis by methionine synthase. Proc. Natl. Acad. Sci., U. S. A.. 100, 3729-3736.
Yamada, K., Strahler, J. R., Andrews, P. C., and Matthews, R. G. (2005) Regulation of human methylenetetrahydrofolate reductase by phosphorylation. Proc. Natl. Acad. Sci. 102 , 10454-10459.
Taurog, R. E., Jakubowski, H., and Matthews, R. G. (2006) Synergistic, random sequential binding of substrates in cobalamin-independent methionine synthase. Biochemistry 45, 5083-5091.
Taurog, R. E., and Matthews, R. G. (2006) Activation of methyltetrahydrofolate by cobalamin-independent methionine synthase. Biochemistry 45, 5092-5102.
Pejchal, R., Sargeant, R., Matthews, R. G., and Ludwig, M. L. (2006) Structural Perturbations in the Ala->Val Polymorphism of Methylenetetrahydrofolate Reductase: How Binding of Folates May Protect Against Inactivation. Biochemistry 45, 4808-4818.
Yamada, K., Gravel, R. A., Toraya, T., and Matthews, R. G. (2006) Human methionine synthase reductase is a molecular chaperone for human methionine synthase. Proc. Natl. Acad. Sci., U. S. A. 103, 9476-9481.