Related Experiment Videos
Organic phosphates increase the solubility of avian haemoglobin D and embryonic chicken haemoglobin
Abstract:
The isolated minor haemoglobin fractions (haemoglobin D) of ostrich, chicken and duck haemoglobin, which constitute about 30% of total intracellular haemoglobin, form crystalline aggregates upon deoxygenation at physiological temperature, ionic strength and pH and at haemoglobin concentrations even well below those present in the red cell. The aggregation is reversed by oxygenation, and can be inhibited by addition of organic phosphates or the corresponding major haemoglobin fraction in a stoichiometric ratio of 1:1. Embryonic haemoglobin from chicken has similar characteristics with respect to its solubility. The results indicate close functional homology of alpha D and embryonic pi-chains as well as a novel role for organic phosphates in the regulation of haemoglobin function.
Insights
Minor hemoglobin fractions (hemoglobin D) in birds form aggregates when deoxygenated. This aggregation is reversible by oxygenation and can be prevented by organic phosphates, suggesting a regulatory role in hemoglobin function.
Area of Science:
- Biochemistry
- Comparative Physiology
- Molecular Biology
Background:
- Minor hemoglobin fractions, specifically hemoglobin D, constitute a significant portion (around 30%) of intracellular hemoglobin in avian species like ostriches, chickens, and ducks.
- These minor fractions exhibit distinct properties compared to the major hemoglobin components.
Purpose of the Study:
- To investigate the aggregation behavior of isolated minor hemoglobin fractions (hemoglobin D) from avian sources.
- To determine the conditions under which aggregation occurs and the factors that can inhibit or reverse it.
- To explore the functional homology between avian alpha D-globin and embryonic pi-globin chains.
Main Methods:
- Isolation of minor hemoglobin fractions (hemoglobin D) from ostrich, chicken, and duck hemolysates.
- Induction of hemoglobin aggregation under physiological conditions (temperature, ionic strength, pH) and varying concentrations.
- Assessment of aggregation reversal by oxygenation.
- Evaluation of the inhibitory effects of organic phosphates and the major hemoglobin fraction on aggregation.
Main Results:
- Isolated avian hemoglobin D fractions spontaneously form crystalline aggregates upon deoxygenation at physiological conditions, even at sub-cellular concentrations.
- Aggregation is fully reversible upon re-oxygenation.
- The addition of organic phosphates or the stoichiometric addition of the corresponding major hemoglobin fraction effectively inhibits this aggregation process.
- Chicken embryonic hemoglobin demonstrates similar solubility characteristics.
Conclusions:
- Avian hemoglobin D exhibits a propensity to aggregate upon deoxygenation, suggesting a potential role in modulating oxygen transport or red blood cell properties.
- The reversibility of aggregation by oxygenation and inhibition by organic phosphates highlight a novel regulatory mechanism for hemoglobin function.
- Functional homology exists between avian alpha D-globin and embryonic pi-chains, indicating conserved molecular mechanisms across developmental stages.