Basic Information

Abstract Number: 1920-3     Author Name: Hassnane Mchaourab Affiliation: Vanderbilt University Session Title: Nitroxide Spin Labels in NMR and ESR Studies of Protein Event Type: Symposia Event Title: Protein Conformational Dynamics from Spin Labeling EPR Spectroscopy Presider(s): Saxena, Sunil Start Time: 03:15 PM ( Slot # 4 ) Date: Wednesday, March 14th, 2012 Location: 207A Keywords: Biospectroscopy, Magnetic Resonance, Membrane, Protein

Abstract Content

Trapping membrane proteins in the confines of a crystal lattice obscures dynamic modes essential for interconversion between multiple conformations in the functional cycle. Moreover, lattice forces could conspire with detergent solubilization to stabilize a minor conformer in an ensemble thus confounding mechanistic interpretation. Spin labeling in conjunction with electron paramagnetic resonance (EPR) spectroscopy offers an exquisite window into membrane protein dynamics in the native–like environment of a lipid bilayer. The main EPR tool is Double Electron-Electron Resonance (DEER) spectroscopy for long range distance measurements between spin label pairs. The average distances from DEER yield the amplitude of protein motion. Furthermore, analysis of the distance distribution can reveal equilibria between multiple conformational intermediates. My laboratory uses spin labeling and EPR spectroscopy to define conformational rearrangements of a broad spectrum of proteins. Specific examples include alternating access in multidrug- and neurotransmitter transporters which exposes the substrate binding site to either side of the membrane and the response of calcium-calmodulin dependent protein kinase to calcium signals, its activation and the structural basis of conformational memory. These studies provide detailed insight into the mechanism of these proteins in a native-like environment in the absence of conformational selectivity imposed by the crystal lattice.