Role of heme in the unfolding and assembly of myoglobin

GuHCl-induced, equilibrium unfolding of five sperm whale metMb variants are measured to understand the discrepancies during the unfolding of wild-type holomyoglobin in the ferric state (metMb). The high affinities of native apoMb (N) for hemin are found to have significant influence on the stability of holo-metMb and the partially unfolded intermediate with hemin bound ((IH) exhibiting a hemichrome spectra are indicative of a bis-histidyl axial coordination which is seen clearly when the stability of the N state or its affinity for hemin is reduced.