Membrane proteins are essential regulators of a number of cellular and physiological processes including signaling between cells, transport across cell membranes and energy transduction processes. High-resolution structures of membrane proteins can provide insight into their function and enable the development of compounds to alter their properties for biological and biomedical purposes. While more than 30% of the human genome and 50% of known drug targets are membrane proteins, few structures of membrane proteins are known. For most membrane proteins, this is due to the lack of membrane mimetics that contain the protein in a stable, functional, and homogeneous state. In this application, we propose to develop robust approaches to produce near-native model membranes that both stabilize membrane-bound proteins or protein-protein complexes in their functional forms and will also enable structure determination at high-resolution by NMR spectroscopy. We have chosen cytochrome proteins (CytP450, CytP450-reductase (CYPOR) and Cytb5) and their complexes (P450-CYPOR and P450- b5) as model systems for optimization. Challenges posed by these membrane proteins are manifold and therefore the biochemical and biophysical approaches developed to tackle these challenges can be relatively easily extended for structural studies of other membrane proteins. To accomplish this goal, we propose to investigate new classes of mild detergents and non-detergent surfactants as well as native membrane-like bicelles that show promise in stabilizing the native fold of membrane proteins using a rapid assignment-free screening process by NMR spectroscopy. While the focus of this proposal is on the rapid optimization of sample conditions for NMR structural studies, the outcome can be extended for investigations using a variety of other biophysical techniques including EPR, FRET and X-ray crystallography.
The outcome of the proposed studies on the production and optimization of membrane proteins will significantly advance our ability to obtain structural and functional insights at atomic-level resolution and will aid in the development of drugs to treat various diseases.
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