Research Interests

I am interested in protein folding and design. Research in my group is currently aimed at finding stably folded variants of myoglobin “circular permuteins”. Myoglobin is a small monomeric heme-containing protein which shares the same folded structure as each of the four subunits in hemoglobin. Hemoglobin is currently under investigation in human clinical trials for indications in blood replacement therapy, and for radiosensitization in cancer treatment. A clinically useful recombinant hemoglobin can be harvested from bacteria in commercial scale facilities.

A “permutein” is a protein mutant in which the order of several amino acids in the protein sequence has been changed. Circular permutation essentially moves the N- and C- termini of the protein to a new location. We are interested in this class of myoglobin mutants for two reason:

1. The folding pathway of myoglobin is well characterized and permuteins will allow us to explore the folding of globins in ways that are not possible with single site mutations. In particular, we are interested in asking how the placement of the N- and C- termini in new locations will affect the folding pathway, and whether constraining the ends of the peptide early in folding is a general solution to the “folding problem”.
2. The therapeutic potential of hemoglobin as an oxygen carrying “drug” (i.e. as a blood replacement, or as an adjunct in radiosensitization) would be expanded if the protein engineering of the hemoglobin molecule could be simplified. Our longer-term goal in this research with permuted myoglobins is to make a single-chain hemoglobin. We intend to use myoglobin as a model for the permutation of hemoglobin (the subunits of hemoglobin are structurally related to myoglobin). We need to know how the “globin fold”, exemplified by myoglobin, tolerates permutation to guide us in the eventual design of a single-chain hemoglobin molecule.

Students in my research group learn how to: clone genes, express mutant proteins in bacteria; purify the mutants, and characterize the folding and stability of the purified proteins by spectroscopic methods (UV-Vis; circular dichroism). Students are also expected to present their results at weekly group meetings, as well as local, and national scientific meetings as appropriate.