Proton nuclear magnetic resonance studies of hemoglobins Osler (β145HC2 Tyr → Asp) and McKees Rocks (β145HC2 Tyr →Term): an assignment for an important tertiary structural probe in hemoglobin
High-resolution proton NMR studies of [human] deoxyhemoglobins Osler (.beta.145HC2 Tyr .fwdarw. Asp) and McKees Rocks (.beta.145HC2 Tyr .fwdarw. Term) indicate that these Hb are predominantely in the oxy quaternary structure in 0.1 M [bis(2-hydroxyethyl)imino]-tris(hydroxymethyl)methane buffer at pH 7. Upon the addition of inositol hexaphosphate, the proton NMR spectra of these Hb became similar to those characteristic of a Hb molecule in the deoxy quaternary structure. The exchangeable proton resonance which is found at -6.4 ppm from H2O in the spectrum of normal human adult deoxyhemoglobin is absent in the spectra of these 2 mutant hemoglobins. Consequently the hydrogen bond between the hydroxyl group of tyrosine-.beta.145HC2 and the carboxyl oxygen of valine-.beta.98FG5 probably gives rise to this resonance. This assignment permits use of the -6.4 ppm resonance as an important tertiary structural proble in the investigation of the cooperative oxygenation of hemoglobin.