Roles of the. beta. 146 histidyl residue in the molecular basis of the Bohr Effect of hemoglobin: A proton nuclear magnetic resonance study

Journal Article · Tue Feb 19 04:00:00 EST 1991 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00221a020· OSTI ID:5510274

Busch, M R; Mace, J E; Ho, N T; Ho, Chien ^[1]

---

1. Carnegie Mellon Univ., Pittsburgh, PA (USA)

Assessment of the roles of the carboxyl-terminal {beta}146 histidyl residues in the alkaline Bohr effect in human and normal adult hemoglobin by high-resolution proton nuclear magnetic resonance spectroscopy requires assignment of the resonances corresponding to these residues. By a careful spectroscopic study of human normal adult hemoglobin, enzymatically prepared des(His146{beta})-hemoglobin, and the mutant hemoglobins Cowtown ({beta}146His {yields} Leu) and York ({beta}146His {yields} Pro), the authors have resolved some of these conflicting results. By a close incremental variation of pH over a wide range in chloride-free 0.1 M N-(2-hydroxyethyl)piperazine-N{prime}-2-ethanesulfonic acid buffer, a single resonance has been found to be consistently missing in the proton nuclear magnetic resonance spectra of these hemoglobin variants. The results indicate that the contribution of the {beta}146 histidyl residues is 0.52 H{sup +}/hemoglobin tetramer at pH 7.6, markedly less than 0.8 H{sup +}/hemoglobin tetramer estimated by study of the mutant hemoglobin Cowtown ({beta}146His {yields} Leu) by Shih and Perutz. They have found that at least two histidyl residues in the carbonmonoxy form of this mutant have pK values that are perturbed, and they suggest that these pK differences may in part account for this discrepancy. The results show that the pK values of {beta}146 histidyl residues in the carbonmonoxy form of hemoglobin are substantially affected by the presence of chloride and other anions in the solvent, and thus, the contribution of this amino acid residue to the alkaline Bohr effect can be shown to vary widely in magnitude, depending on the solvent composition. These results demonstrate that the detailed molecular mechanisms of the alkaline Bohr effect are not unique but are affected both by the hemoglobin structure and by the interactions with the solvent components in which the hemoglobin molecule resides.

• OSTI ID: 5510274
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 30:7; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
AZOLES
BARYONS
BOHR THEORY
CARBON 13
CARBON ISOTOPES
CARBOXYLIC ACIDS
ELEMENTARY PARTICLES
ELEMENTS
EVEN-ODD NUCLEI
FERMIONS
GLOBINS
HADRONS
HEMOGLOBIN
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HISTIDINE
IMIDAZOLES
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
METABOLISM
NMR SPECTRA
NONMETALS
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN
PIGMENTS
PORPHYRINS
PROTEINS
PROTONS
RESONANCE
SPECTRA
STABLE ISOTOPES