This project is intended to provide fundamental information on the molecular mechanisms which control binding of oxygen and other ligands to hemoglobins. High resolution NMR methods will be used to investigate the heme pocket conformations and dynamics of several monomeric hemoglobins and myoglobins. These are the simplest proteins capable of reversible oxygenation and are excellent models for understanding the structural basis for control of ligand binding by tetrameric vertebrate hemoglobins. Tetrameric hemoglobins are not amenable to such a comprehensive NMR analysis as proposed in this project. The project will comprise a systematic investigation and comparison of a series of monomeric hemoglobins and myoglobins which vary widely in their oxygen affinities (or more importantly, in the kinetics of their oxygen association and dissociation reactions). A detailed description of the conformations, structural fluctuations and side chain dynamics of these proteins will be sought. Comparative information on the structure and dynamics of the heme pockets and ligand access channels is of particular importance. Attention will be focused on diamagnetic complexes. Two dimensional NMR techniques will be used extensively. Studies of conformation will be based on measurements of ring current shifts, nuclear Overhauser effects and coupling constants. Amide proton exchange rates and nuclear relaxation rates (primarily 13C) will provide information on protein structural fluctuations and side chain dynamics.
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