Interaction of fully liganded valency hybrid hemoglobin with inositol hexaphosphate. Implication of the IHP-induced T state of human adult methemoglobin in the low-spin state.
To gain further insight into the quaternary structures of methemoglobin derivatives in the low-spin state, the interaction of fully liganded valency hybrid human hemoglobins with IHP was studied by proton NMR spectroscopy. Upon addition of IHP to (alpha CO beta + N3-)2, the same resonances as the previously reported IHP-induced NMR peaks for azidomethemoglobin (alpha + N3-beta +N3-)2 appeared, whereas the binding of IHP did not significantly affect the NMR spectra for (alpha + N3-beta CO)2. The binding of IHP also brought about more pronounced spectral changes for (alpha CO beta + Im)2 and (alpha CO beta + H2O)2 than for (alpha + Im beta CO)2 and (alpha + H2O beta CO)2. Therefore, the IHP-induced NMR peaks for azidomethemoglobin are attributed to the beta heme methyl group. Such IHP-induced beta heme methyl resonances were also observed for (alpha NO beta + N3-)2, which undergoes quaternary structural change, analogously to the R-T transition by the binding of IHP. From the above results, it was suggested that the IHP-induced heme methyl resonances for azidomethemoglobin and (alpha CO beta +N3-)2 may also be associated with the quaternary structure of these Hbs, implying the presence of the IHP-induced "T-like" state in low-spin metHb A.
D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008706:Methemoglobin / Q000031:analogs & derivatives* / Q000378:metabolism; D010833:Phytic Acid / Q000494:pharmacology*; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization
D006454:Hemoglobins; D008024:Ligands; C029387:methemoglobin azide; D010833:Phytic Acid; D008706:Methemoglobin