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Ligand binding and stereochemical effects in hemocyanins
M Brunori1, H A Kuiper, L Zolla
1Institute of Chemistry and CNR Centre for Molecular Biology, Faculty of Medicine, University of Rome, 00185 Rome, Italy.
The EMBO Journal
|January 1, 1982
Summary
Oxygen binding to Helix pomatia beta-hemocyanin involves an allosteric transition, unlike carbon monoxide binding. This difference highlights unique cooperativity mechanisms in hemocyanins compared to hemoglobins.
Area of Science:
- Biochemistry
- Protein Science
- Comparative Physiology
Background:
- Hemocyanins and hemoglobins are oxygen-binding proteins with distinct chemical structures.
- Understanding hemocyanin allostery provides insights into respiratory pigment evolution.
Purpose of the Study:
- To investigate the Bohr effect in Helix pomatia beta-hemocyanin.
- To compare oxygen and carbon monoxide binding mechanisms.
Main Methods:
- Potentiometric titration was used to estimate the Bohr effect.
- Analysis of oxygen and carbon monoxide binding affinities.
Main Results:
- Oxygen binding is associated with a quaternary allosteric transition (T-->R).
- Carbon monoxide binding does not induce this transition.
- Homotropic interactions are specific to oxygen binding in hemocyanins.
Conclusions:
- Hemocyanin cooperativity is initiated by oxygen's stereochemical requirements, forming a bridge between copper atoms.
- Hemocyanin oxygen binding differs significantly from hemoglobin, despite shared features.
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