Lacking deoxygenation‐linked interaction between cytoplasmic domain of band 3 and HbF from fetal red blood cells

Abstract

Several of the red blood cell's metabolic and membrane functions display dependence on haemoglobin oxygenation. In adult human red cells, the increased glycolytic rate at low O2 tension results from binding of deoxygenated HbA at negatively charged, N-terminal, cytoplasmic domain of the membrane protein band 3, which liberates glycolytic enzymes from this site. This study aims to investigate the role of fetal HbF (that has lower anion-binding capacity than HbA) in fetal red cells (that are subjected to low O2 tensions), and to elucidate possible linkage (e.g. via the major red cell membrane organising centre, band 3) between the individual oxygenation-linked reactions encountered in red cells. The interaction between band 3 and Hb is analysed in terms of the effects, measured under different conditions, of a 10-mer peptide that corresponds to the N-terminus of human band 3 protein, on the oxygenation reaction of HbF and HbA, isolated from umbilical chord red cells. Contrasting with the unequivocal interaction of the peptide with HbA that with fetal HbF is weak, and annihilated in the presence of autochthonous red cell O2 affinity modulators (chloride and organic phosphates). The data indicate that HbF does not function as a transducer mediating O2 dependence of glycolysis in fetal red cells, in accordance with the different O2 and metabolic profiles compared to those in HbA-bearing adult red cells. In conjunction with the previously discovered O2 dependence of K+ transport in HbF-rich fetal cells, they moreover argue against linkage between different, physiologically relevant, O2-dependent red cell functions.