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Striped mullet (Mugil cephalus) hemoglobin system: multiplicity and functional properties
Alessandra Olianas1, Claudia Meloni, Irene Messana
1Department of Sciences Applied to Biosystems, University of Cagliari, Cittadella Universitaria, 09042, Monserrato (CA), Italy.
Summary
Mugil cephalus hemoglobin exhibits complex heterogeneity with multiple globin chains. Organic phosphates like GTP bind to two distinct sites, with chloride ions influencing binding affinity and competition.
Area of Science:
- Biochemistry
- Molecular Biology
- Fish Physiology
Background:
- Hemoglobin heterogeneity is common in fish, potentially linked to adaptation.
- Mugil cephalus (striped red mullet) displays a predominant hemoglobin phenotype.
Purpose of the Study:
- To characterize the molecular composition and oxygen-binding properties of M. cephalus hemoglobins.
- To investigate the binding of guanosine triphosphate (GTP) to hemoglobin.
Main Methods:
- Ion-exchange chromatography and reverse-phase HPLC for hemoglobin separation.
- Electrospray ionization-mass spectrometry for globin chain identification.
- Oxygen-binding experiments to assess Bohr and Root effects, and GTP binding.
Main Results:
- HbI comprises two beta (β1, β3) and two alpha (α1, α2) globin chains; HbII contains one beta (β2) and the same alpha chains.
- Both hemoglobin components exhibit similar oxygen-binding properties, including Bohr and Root effects.
- Hemoglobin possesses two GTP-binding sites, with chloride ions competing for these sites.
Conclusions:
- M. cephalus hemoglobin heterogeneity involves multiple globin chains with conserved oxygen-binding characteristics.
- GTP binding is influenced by chloride ions, suggesting complex allosteric regulation.
- Hemoglobin heterogeneity in fish may arise from factors beyond simple evolutionary adaptation to environmental needs.
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