TY - JOUR
T1 - 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
T2 - Hemoglobins Presbyterian and Yoshizuka
AU - O'Donnell, J. K.
AU - Birch, P.
AU - Parsons, C. T.
AU - White, S. P.
AU - Okabe, J.
AU - Martin, M. J.
AU - Adams, C.
AU - Sundarapandiyan, K.
AU - Manjula, B. N.
AU - Acharya, A. S.
AU - Logan, J. S.
AU - Kumar, R.
N1 - Copyright:
Copyright 2004 Elsevier B.V., All rights reserved.
PY - 1994
Y1 - 1994
N2 - 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.
AB - 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.
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M3 - Article
C2 - 7961689
AN - SCOPUS:0028032586
VL - 269
SP - 27692
EP - 27699
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 44
ER -