[ Research Interests ] [ Representative Publications ]

Douglas Barrick Professor Department of Biophysics Department of Biology Adjunct Professor Department of Biology B.A. University of Colorado Ph.D. Stanford University

Department of Biophysics Johns Hopkins University 3400 North Charles Street Baltimore, MD 21218-2685 U.S.A. Office Telephone: Lab Telephone: Department Fax: Email: 410.516.0409 410.516.7149 410.516.4118 barrick@jhu.edu   Office: Jenkins 214 Lab: Jenkins 205/212/213

Research Interests Determination of an Atomic-level Description of Protein Structure and Function : 1.) How do proteins fold? 2.) How do folded proteins assemble into regulated multiprotein complexes? 3.) How did proteins evolve? To address the questions of how proteins evolved and how they fold, we are studying a class of modular proteins that contain simple, repetitive architectures. These proteins are built from simple units of supersecondary structure that are repeated in multiple, tandem copies. Examples include ankyrin repeats and leucine-rich repeats, as illustrated below: This simple, modular architecture compared to globular proteins (see ribonuclease, top) provides a unique framework in which to understand protein folding thermodynamics and kinetics. Since repeat-proteins are linear, they provide an excellent system to determine the maximum radius of coupling between elements of protein structure, and are amenable to statistical thermodynamic modeling to help us quantify the origin and extent of coupling. And since the close contacts in repeat-proteins are made exclusively from neighboring segments of the polypeptide, their kinetics of folding should be fast, based on current ideas relating topology to folding rates.  Moreover, they provide an excellent test-bed for predictions of folding based on simplified models.  We are using deletion and point substitutions to map the equilibrium energy landscape of repeat proteins, and map kinetic flux onto these surfaces.  We are also taking advantage of the linear architecture of to explore mechanical unfolding via atomic force microscopy. This simple architecture also suggests a major simplification to the evolutionary origins of proteins. Through recombination events, the simple building blocks illustrated above can be duplicated, fused, and mixed, providing a route to large proteins with diverse sequences, bypassing the need to start from large (and improbable) folded domains. We are currently looking at the effects of deletion, insertion, and recombination on stability and structure formation in repeat proteins. These measurements will provide us with an assessment of the fitness of such recombinant constructs.  In addition, such rearrangements provide a route to design novel platforms for binding and catalysis. Finally, we are studying how proteins assemble into regulated multiprotein complexes using a system that is critical for transmembrane signal transduction, the Notch pathway. The Notch pathway controls cellular differentiation during development, and disruption of normal function in humans has been implicated in stroke, dementia, and in certain forms of leukemia. Our goal is to determine how the Notch receptor and its intracellular effectors interact, both structurally and thermodynamically, using techniques such as spectroscopy, analytical ultracentrifugation, calorimetry, and x-ray crystallography. Through studies of interactions between different components of this pathway, we hope to identify key allosteric regulatory mechanisms that control signaling, with the ultimate goal of describing the signal transduction process in terms of a binding partition function. Representative Publications Bergagna, A., Toptygin, D., Brand, L., and Barrick, D. 2008. The effects of conformational heterogeneity on the binding of the Notch intracellular domain to effector proteins: a case of biologically tuned disorder.  Biochem. Soc. Trans. 36, in press. Courtemanche, N., and Barrick, D. 2008. Folding thermodynamics and kinetics of the Leucine-rich repeat domain of the virulence factor Internalin B.  Protein Science 17, 43-53. Kloss, E., Courtemanche, N., & Barrick, D. 2007. Repeat-protein folding: new insights into origins of cooperativity, stability, and topology.  Archives of Biochemistry and Biophyics 469, 83-99. Lubman, O.Y., Ilagan, M.X.G., Kopan, R., and Barrick, D. 2007. Quantitative Dissection of the Notch:CSL Interaction: Insights into the Notch Transcriptional Switch. J. Mol. Biol. 365, 577-589. Bradley, C.M. and Barrick, D. 2006. The Notch Ankyrin Domain Folds Through a Discrete, Centralized Pathway. Structure 14, 1303-1312. Street, T.O., Rose, G.D., and Barrick, D. 2006. The Role of Introns in Repeat-Protein Gene Formation. J. Mol. Biol. 360, 258-266. Zweifel, M.E., Leahy, D.J., and Barrick, D. 2005. Structure and Notch-receptor binding of the tandem WWE domain of Deltex. Structure 13, 1599-1611. Mello, C., Bradley, C.M., Tripp, K.W., and Barrick, D. 2005. Experimental Characterization of the Folding Kinetics of the Notch Ankyrin Domain. J. Mol. Biol. 352, 266-281. Mello, C., and Barrick, D. 2004. An experimentally determined protein folding energy landscape. Proc. Natl. Acad. Sci. USA 101, 14102-14107. Zweifel, M.E., Leahy, D.J, Hughson, F.M., and Barrick, D. 2003. Structure and stability of the ankyrin domain of  the Drosophila Notch receptor.  Protein Science 12, 2622-2632.

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