Department of Chemistry and Biochemistry (Conference/Workshop/Seminar)
Karen G. Fleming, T.C. Jenkins Department of Biophysics, John Hopkins University, Baltimore, Maryland, will present a seminar entitled, "The Versatile beta-Barrel Gives Up a Novel Hydrophobicity Scale and Other Secrets of the Membrane".
The protein-folding problem is one of the contemporary challenges of biophysics. Knowing how the sequence encodes a native structure will provide insight into how genetic mutations cause disease, how protein sequences evolve and will provide a tool to design proteins with novel functions. While the folding of soluble proteins has been studied for decades, studies on membrane proteins are not as common. We have recently developed protocols to measure the stabilities of three transmembrane proteins: OmpLA, PagP and OmpW.
We have used OmpLA as a scaffold to experimentally discover a novel hydrophobicity scale that reveals the transfer free energies of the twenty natural amino acid side chains from water to a central position in phospholipid bilayers. Our measurements reveal parity for apolar side-chain contributions between soluble and membrane proteins and demonstrate that an arginine side-chain placed near the middle of a lipid bilayer is accommodated with much less energentic cost than previously predicted.
In comparing the stabilities of all three proteins, the absolute values of our stability measurements suggest that the folding free energies for these membrane proteins may be the thermodynamic sink that establishes an energy gradient across the periplasm. this potential thus drives the sorting of outer membrane proteins by chaperones to the outer membranes in living bacteria. Binding free energies of these outer membrane proteins with periplasmic chaperones support this energy sink hypothesis.
Department of Chemistry and Biochemistry
Wendy J. Leach email@example.com
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