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Carbon dioxide binding to human hemoglobin cross-linked between the alpha chains
K D Vandegriff1, L Benazzi, M Ripamonti
1Division of Blood Research, Letterman Army Institute of Research, Presidio of San Francisco, California 94129-6800.
The Journal of Biological Chemistry
|February 15, 1991
Summary
Cross-linking human hemoglobin (Hb) between Lys alpha 99 residues reduces carbon dioxide (CO2) binding capacity and affinity. This modification specifically hinders CO2 interaction with the alpha-subunit N-termini.
Area of Science:
- Biochemistry
- Physiological Chemistry
Background:
- Human hemoglobin (Hb) exhibits distinct binding sites for carbon dioxide (CO2), involving amino-terminal valines of alpha and beta chains.
- Understanding CO2 binding to Hb is crucial for studying respiratory gas transport and physiological pH regulation.
Purpose of the Study:
- To investigate the effect of cross-linking human hemoglobin between Lys alpha 99 residues on carbon dioxide binding.
- To determine how this cross-linking modification alters CO2 affinity and the ligand-linked effect.
Main Methods:
- Manometric techniques were employed to measure carbon dioxide binding to unmodified and cross-linked human hemoglobin.
- Data were analyzed using binding models to quantify affinity constants and site capacities.
Main Results:
- Cross-linked hemoglobin demonstrated reduced CO2 binding compared to native Hb across all CO2 concentrations and ligand states.
- The ligand-linked effect on CO2 binding was diminished in the cross-linked Hb.
- Analysis indicated that cross-linking at Lys alpha 99 prevents CO2 binding at the alpha-subunit NH2 termini, reducing overall CO2 saturation.
Conclusions:
- Cross-linking human hemoglobin at Lys alpha 99 significantly impairs CO2 binding, particularly at the alpha-subunit N-termini.
- This modification alters the affinity and capacity of hemoglobin for carbon dioxide, impacting its physiological role in gas transport.