The Skaggs Institute
for Chemical Biology
Synthetic Protein Engineering
P.E. Dawson, F. Brunel, M. Churchill, A. Dirksen, F.G. Hansen, N. Metanis, S. Shekhter, C. Schroeder, T. Tiefenbrunn
We use synthetic
chemistry to synthesize and chemically modify biological macromolecules. Much of
our work centers on proteins and the development of efficient methods to assemble
large polypeptides in aqueous solution without the use of protecting groups. Using
these chemoselective ligation techniques, we are able to chemically synthesize not
only fully functional natural proteins but also proteins with elements of structure
and function that do not occur naturally. This powerful synthetic access to proteins
facilitates the fine-tuning of amino acid side chains
to achieve proteins with
greater conformational stability or proteins with altered or improved binding specificity
and catalytic activity.
several of our projects, we focus directly on therapy for human diseases. For example,
we are collaborating with D.R. Burton, Scripps Research, and I.A. Wilson, the Skaggs
Institute, to develop potential HIV vaccines based on the membrane proximal region
of the gp41 glycoprotein. In addition, we hope to use synthetic protein chemistry
to engineer stabilized protein-based HIV microbicides to prevent infection. Similarly,
we are developing the methods necessary to use traditional medicinal chemistry techniques
to develop more efficient protein therapeutics for the treatment of cancer. Finally,
we are using our insights into the chemistry of thioester functional groups to better
understand protein palmitoylation, which is critical for the development of therapeutic
approaches for infantile Batten disease.
Synthetic protein chemistry also enables
us to make the specific, subtle changes to the structure of a protein required to
address basic questions about how proteins function. For example, we have used a
simple amide-to-ester replacement in the polypeptide backbone of proteins to study
the thermodynamics and kinetics of protein folding. We are using such backbone-modified
proteins to address the role of hydrogen bonding and secondary structure formation
in proteins such as chymotrypsin inhibitor 2, IgG-binding proteins, and acylphosphatase.
In collaboration with F.E. Romesberg, Scripps Research, we are using synthetic chemistry
to incorporate deuterium at specific sites to enable direct observation of protein
vibrations by infrared spectroscopy. These approaches are also being used to probe
the molecular basis of enzymatic activity. For example, we have probed the role
of electrostatic interactions in 4-oxaloacetate tautomerase and the effects of selenocysteine
in the oxidoreductase glutaredoxin. In future studies, we will probe the role of
dynamics in the catalytic activity of these enzymes.
Brunel, F.M., Zwick, M.B., Cardoso,
R.M., Nelson, J.D., Wilson, I.A., Burton, D.R., Dawson, P.E.
Structure-function analysis of the epitope for 4E10, a broadly neutralizing human
immunodeficiency virus type 1 antibody. J. Virol. 80:1680, 2006.
Cremeens, M.E., Fujisaki, H., Zhang,
Y., Zimmermann, J., Sagle, L.B., Matsuda, S., Dawson, P.E., Straub, J.E., Romesberg,
F.E. Efforts toward developing
direct probes of protein dynamics. J. Am. Chem. Soc. 128:6028, 2006.
Delehanty, J.B., Medintz, I.L., Pons,
T., Brunel, F.M., Dawson, P.E., Mattoussi, H. Self-assembled
quantum dot-peptide bioconjugates for selective intracellular delivery. Bioconjug.
Chem. 17:920, 2006.
Medintz, I.L., Clapp, A.R., Brunel,
F.M., Tiefenbrunn, T., Uyeda, H.T., Chang, E.L., Deschamps, J.R., Dawson, P.E.,
Mattoussi, H. Proteolytic
activity monitored by fluorescence resonance energy transfer through quantum-dot-peptide
conjugates. Nat. Mater. 5:581, 2006.
Sagle, L.B., Zimmermann, J., Matsuda,
S., Dawson, P.E., Romesberg, F.E. Redox-coupled
dynamics and folding in cytochrome c. J. Am. Chem. Soc. 128:7909. 2006.