Proton nuclear magnetic resonance studies of hemoglobins Osler (beta145HC2 Tyr replaced by Asp) and McKee Rocks (beta145HC2 Tyr replaced by term): an assignment for an important tertiary structural probe in hemoglobin

Abstract

High-resolution proton nuclear magnetic resonance studies of deoxyhemoglobins Osler (beta145HC2 Tyr replaced by Asp) and McKees Rocks (beta 145HC2 Tyr replaced by term) indicate that these hemoglobins are predominately 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 nuclear magnetic resonance spectra of these hemoglobins become similar to those characteristic of a hemoglobin 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 two mutant hemoglobins. Consequently we believe the hydrogen bond between the hydroxyl group of tyrosine-beta145HC2 and the carboxyl oxygen of valine-beta98FG5 gives rise to this resonance. This assignment allows us to use the -6.4ppm resonance as an important tertiary structural probe in the investigation of the cooperative oxygenation of hemoglobin.