Modeling heme protein active sites with the his93gly cavity mutant of sperm whale myoglobin: complexes with nitrogen-, oxygen- and sulfur-donor proximal ligands

Abstract

Recent investigations of the His93Gly (H93G) "cavity" mutant of myoglobin as a versatile scaffold for modeling heme states are described. The difference in accessibility of the two sides of the heme in H93G myoglobin makes it possible to generate mixed ligand adducts in the ferric state that are difficult to prepare with heme models in organic solvents. In addition, the protection provided to the heme by the protein environment allows for the preparation of stable oxyferrous and oxo-iron(IV) complexes at near-ambient temperatures with variable ligands trans to the normally reactive dioxygen and oxo substituents. The extensive range of possible complexes that can be generated using the H93G system is illustrated with examples involving imidazole, phenolate, benzoate, thiolate and thiol ligands bound to the proximal side of the heme iron.