Professor of Biochemistry and Chemistry
Ph.D., Boston University
Our interests are generally in the relationship of protein three-dimensional structure to chemical function. To this end, research is focussed on the modification of the catalytic properties of a number of pharmaceutically or industrially important enzymes. The methods used are a combination of X-ray crystallography, design of transition-state analog inhibitors, and site-directed mutagenesis. The objectives are to learn how to re-engineer these catalysts to perform useful chemical reactions which may not occur efficiently with the naturally occurring enzyme, to dissect the individual steps in a mechanism and characterize them structurally, or to learn how to inhibit an enzyme specifically and selectively.
The proteins being studied currently include enzymes utilizing pyridoxal phosphate as cofactor, a GTP-binding protein, a DNA-binding protein, and several proteases. Different methods are being used to study these systems, including traditional kinetic and structural methods, and low-temperature and time-resolved x-ray structural methods. In addition, a new method for mapping of binding surfaces on proteins is being developed for the design of specific inhibitors.
Pyridoxal is capable of catalyzing several types of transformations. However, any one enzyme utilizing this cofactor does only one of them predominantly. The question therefore arises how the protein controls the chemical outcome of such transformations. We are studying a number of these enzymes structurally in order to begin to answer that question.
The expression of diphtheria toxin in toxigenic Corynebacterium diphtheria is controlled by a transition metal ion activated repressor DtxR. The repressor binds DNA after activation by the metal ion and thereby regulates expression of the toxin. The mechanism of activation is being studied structurally.
Serine proteases are important in cellular development, blood clotting, and a variety of defense mechanisms. Disorders involving these proteases are often linked to the absence or inefficiency of a specific inhibitor to control the activity of the enzyme. The design of such inhibitors requires detailed knowledge of the structure of the enzyme, of the enzyme complexed with inhibitors, and if possible, an understanding of the mechanisms of inhibition.
See a complete list of Ringe's publications.
Decreased Sensitivity to Changes in the Concentration of Metal Ions as the Basis for the Hyperactivity of DtxR(E175K). D'Aquino JA, Denninger AR, Moulin A, D'Aquino KE, Ringe D. J Mol Biol. 2009 May 8.
Snapshot of a reaction intermediate: analysis of benzoylformate decarboxylase in complex with a benzoylphosphonate inhibitor. Brandt GS, Kneen MM, Chakraborty S, Baykal AT, Nemeria N, Yep A, Ruby DI, Petsko GA, Kenyon GL, McLeish MJ, Jordan F, Ringe D. Biochemistry. 2009 Apr 21;48(15):3247-57. PMID: 19320438