Structural dynamics in the active site of murine neuroglobin and its effects on ligand binding.

摘要: We have examined the effects of active site residues on ligand binding to heme iron mouse neuroglobin using steady-state and time-resolved visible spectroscopy. Absorption spectra native protein, mutants H64L K67L double mutant H64L/K67L were recorded for ferric ferrous states over a wide pH range (pH 4-11), which allowed us identify number different species with ligands at sixth coordination, characterize their spectroscopic properties, determine pK values residues. In flash photolysis experiments CO-ligated samples, reaction intermediates competition coordination studied. These data provide insights into structural changes in role key His64 Lys67. interferes exogenous access iron. Lys67 sequesters distal pocket from solvent. The is very reactive, as inferred fast kinetics ability bind water or hydroxyl heme. Fast bond formation favors geminate rebinding; yet large fraction bimolecular rebinding observed implies that escape highly efficient. Even slight variations cause pronounced association rate near physiological pH, may be important functional processes.