Terrence G. Oas

Associate Professor of Biochemistry and Chemistry

Protein folding; structure-function relationships of proteins; multidimensional NMR structure determination of macromolecules.

Contact Information

Office Number: (919) 684-4363

Fax: (919) 681-8862

e-mail oas@duke.edu

Lab Location

Room 230 Nanaline Duke

Mailing Address

Department of Biochemistry

230C Nanaline Duke Building

Box 3711, DUMC

Durham, NC 27710

Education

• Ph.D. (University of Oregon, 1986)

Research Interests

Our laboratory is primarily interested in the mechanisms of protein folding. We use nuclear magnetic resonance (NMR) and other types of spectroscopy to study the solution structure, stability and folding reactions of small protein models. In the past few years, our work has primarily focused on a monomeric form of the DNA-binding protein, λ repressor. This protein (λ_6-85) is a stable, native protein that folds in a two-state fashion, i.e. only two states, fully denatured or fully native are populated under all conditions. Using a dynamic NMR method, we have shown that λ_6-85 folds in less than 300 msec and a hyperstable mutant form (G46A,G48A) folds in 15 msec under physiological conditions. Both the wild type and mutant forms unfold very rapidly with a native state lifetime of only 30 milliseconds. Thus, under physiological conditions, the N-terminal domain samples the unfolded state 30 times per second. Clearly, for this protein and a growing number of other rapidly folding and unfolding proteins, folding is more than a once-in-a-lifetime process, it happens millions of times during the lifetime of the protein in the cell.

We have developed a quantitative and predictive model for the folding mechanism of λ_6-85 based on diffusion-collision theory. This model correctly predicts the folding rates of several λ_6-85 variants that we have characterized experimentally and we are in the process of testing and refining the model with other variants. The mechanism of λ_6-85 folding envisioned by the model involves a large ensemble of pathways by which the five native helices form transiently, diffuse and collide to form native inter-helical contacts.

We are also interested in the dynamic properties of native proteins in solution. We study the motions of proteins over the picosecond to millisecond time scale using a variety of NMR-based experiments including ¹⁵N relaxation studies, amide hydrogen exchange rates and dynamic NMR. With these results we hope to gain a better understanding of the dynamic behavior of proteins in solution and the role of these dynamics in function.

Most recently, we have begun to characterize the folding of the protein subunit of Bacillus subtilis Ribonuclease P, are ribonulceoprotein that catalyzes the cleavage of precursor tRNAs to their mature form. Purified B. subtilis P protein is unfolded under physiological conditions but can be refolded by the addition of small molecule ligands at micromolar concentrations. This tightly coupled folding and binding may play an important role in the assembly of the protein-RNA complex that forms the active RNase P holoenzyme. We are in the process of characterizing the ligand selectivity, binding affinities and energetics and kinetics of P protein binding and folding.

Selected Publications