Influence of the chemical nature of side chain at β108 of hemoglobin A on the modulation of the oxygen affinity by chloride ions. Low oxygen affinity variants of human hemoglobin expressed in transgenic pigs: Hemoglobins Presbyterian and Yoshizuka

J. K. O'Donnell, P. Birch, C. T. Parsons, S. P. White, J. Okabe, M. J. Martin, C. Adams, K. Sundarapandiyan, B. N. Manjula, A. S. Acharya, J. S. Logan, R. Kumar

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23 Scopus citations

Abstract

Hemoglobin A (HbA) and two low oxygen affinity variants of HbA, Hb(Presbyterian) and Hb(Yoshizuka), were produced in transgenic pigs and purified to homogeneity by ion-exchange chromatography. These two variants contain either lysine (Hb(Presbyterian)) or aspartic acid (Hb(Yoshizuka)) instead of the normal asparagine residue at position β108 in HbA. Transgenic pigs expressed these variants at a level up to 11% and were healthy. Both Hb(Presbyterian) and Hb(Yoshizuka) exhibited low O2 affinity (P50 of 21.2 and 18.9, respectively, compared with control HbA value of 11.8 in 0.1 M NaCl, pH 7.5) and retained normal cooperativity with Hill coefficients of 2.9 and 2.5, respectively. Hb(Presbyterian) exhibited Bohr effect comparable with HbA. In contrast, Hb(Yoshizuka) had a diminished response to changes in pH. Thus the structural basis of reduced O2 affinity of these variants appears to be distinct: the consequence of mutation at β108 is a function of the chemical nature of the side chain. This is further confirmed by the sensitivity of the O2 affinity of the variants to the presence of Cl-. The O2 affinity of Hb(Yoshizuka) is insensitive to changes in Cl- concentration, whereas the O2 affinity of Hb(Presbyterian) exhibited a pronounced and dramatic chloride effect. In fact, P50 of Hb(Presbyterian) was identical to that of HbA at very low Cl- concentrations, and the P50 increased to >40 at 0.5 M Cl-. The chloride effect was completely abolished when Hb(Presbyterian) was stabilized at the 2,3-diphosphoglycerate pocket by interdimeric cross-linking. Molecular modeling studies demonstrate that in Hb(Presbyterian), Cl- can bridge the ε-amino group of Lys(β108) with either the guanidino group of Arg(β104) or the ε-amino group of Lys(α99), resulting in the stabilization of the 'T' structure. The utility of these low O2 affinity hemoglobins as cell-free oxygen carriers is discussed.

Original languageEnglish (US)
Pages (from-to)27692-27699
Number of pages8
JournalJournal of Biological Chemistry
Volume269
Issue number44
StatePublished - Jan 1 1994

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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    O'Donnell, J. K., Birch, P., Parsons, C. T., White, S. P., Okabe, J., Martin, M. J., Adams, C., Sundarapandiyan, K., Manjula, B. N., Acharya, A. S., Logan, J. S., & Kumar, R. (1994). Influence of the chemical nature of side chain at β108 of hemoglobin A on the modulation of the oxygen affinity by chloride ions. Low oxygen affinity variants of human hemoglobin expressed in transgenic pigs: Hemoglobins Presbyterian and Yoshizuka. Journal of Biological Chemistry, 269(44), 27692-27699.