Tryptophan fluorescence of human hemoglobin II. Effect of inositol hexaphosphate on the T-R transition

Abstract

Fluorescence spectra of tryptophan residues of human hemoglobin in the absence and presence of inositol hexaphosphate were measured at room temperature. The tryptophan fluorescence intensity of deoxy HbA was observed to decrease in accordance with the binding with inositol hexaphosphate. The fluorescence intensity of HbA, Hb Kempsey (β99 Asp-Asn), Hb Chesapeake (α92 Arg-Leu) and NES-des-Arg Hb (des-141α Arg and β93 Cys- N-ethylsuccinimide derivative) in the presence of inositol hexaphosphate exhibits a considerable decrease in the deoxy to oxy transition, while no or slight fluorescence intensity change was observed in the deoxy to oxy transition of Hb Kempsey and NES-des-Arg Hb in the absence of inositol hexaphosphate. The tryptophan fluorescence behavior suggests that the inositol hexaphosphate-induced structural change in these hemoglobins is attributable to the formation of a different T type of structure from that of the normal T-R transition.