TY - JOUR
T1 - Oxygen binding to fallow-deer (Dama dama) hemoglobin
T2 - Stepwise enthalpies at pH 7.4
AU - Johnson, Craig R.
AU - Angeletti, Mauro
AU - Pucciarelli, Stefania
AU - Freire, Ernesto
N1 - Funding Information:
This work was supported by NIH grant RR-04328, GM-379 11, NS-24520.
PY - 1996/3/7
Y1 - 1996/3/7
N2 - High-precision thin-layer gas-solution microcalorimetry has been used to study the oxygen binding properties of fallow-deer (Dama dama) hemoglobin under physiological conditions. This method measures directly the enthalpy of macromolecular ligand binding by changing the ligand activity in a manner analogous to that of the Gill thin-layer optical apparatus ([1], D. Dolman and S.J. Gill, Anal. Biochem., 87 (1978) 127-134). By logarithmically lowering the partial pressure of oxygen we have generated differential heat binding curves of oxygen binding to fallow-deer hemoglobin in phosphate buffer at pH 7.4. In order to enlarge the data field, the temperature dependence of the oxygen affinity was examined by generating binding curves at a number of different temperatures allowing for separation of enthalpy and free energy parameters. This type of experimental analysis makes no assumption of optical linearity between the various heme groups and reveals initially that overall oxygen binding to fallow-deer hemoglobin is less exothermic and of lower affinity than for human hemoglobin A,. In addition, previous optical work on the ancestrally related reindeer hemoglobin (Rangifer tarandus; [2], B. Giardina, O. Brix, M. Nuutinen, S. Sherbini, A. Bardgard, G. Lazzarino and S. Condo, FEES Lett., 247 (1989) 135) has indicated that the enthalpy associated with its final two oxygen binding steps is minimal. Our calorimetric determination with fallow-deer hemoglobin also reveals this tendency. Presumably, this adaptation would make it easier for these animals to maintain a consistent hemoglobin oxygen saturation level under environmental conditions where the temperature fluctuates.
AB - High-precision thin-layer gas-solution microcalorimetry has been used to study the oxygen binding properties of fallow-deer (Dama dama) hemoglobin under physiological conditions. This method measures directly the enthalpy of macromolecular ligand binding by changing the ligand activity in a manner analogous to that of the Gill thin-layer optical apparatus ([1], D. Dolman and S.J. Gill, Anal. Biochem., 87 (1978) 127-134). By logarithmically lowering the partial pressure of oxygen we have generated differential heat binding curves of oxygen binding to fallow-deer hemoglobin in phosphate buffer at pH 7.4. In order to enlarge the data field, the temperature dependence of the oxygen affinity was examined by generating binding curves at a number of different temperatures allowing for separation of enthalpy and free energy parameters. This type of experimental analysis makes no assumption of optical linearity between the various heme groups and reveals initially that overall oxygen binding to fallow-deer hemoglobin is less exothermic and of lower affinity than for human hemoglobin A,. In addition, previous optical work on the ancestrally related reindeer hemoglobin (Rangifer tarandus; [2], B. Giardina, O. Brix, M. Nuutinen, S. Sherbini, A. Bardgard, G. Lazzarino and S. Condo, FEES Lett., 247 (1989) 135) has indicated that the enthalpy associated with its final two oxygen binding steps is minimal. Our calorimetric determination with fallow-deer hemoglobin also reveals this tendency. Presumably, this adaptation would make it easier for these animals to maintain a consistent hemoglobin oxygen saturation level under environmental conditions where the temperature fluctuates.
KW - Allosteric interactions
KW - Calorimetry
KW - Cooperativity
KW - Hemoglobin
KW - Molecular adaptation
KW - Oxygen binding
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U2 - 10.1016/0301-4622(95)00140-9
DO - 10.1016/0301-4622(95)00140-9
M3 - Article
C2 - 8867331
AN - SCOPUS:0030012769
SN - 0301-4622
VL - 59
SP - 107
EP - 117
JO - Biophysical Chemistry
JF - Biophysical Chemistry
IS - 1-2
ER -