A possible new mechanism of oxygen affinity modulation in mammalian hemoglobins.

Bovine red cells do not contain appreciable amounts of 2,3-diphosphoglycerate (2,3-DPG). Bovine hemoglobin, however, has a particular sensitivity to chloride ions and as a result it can attain oxygen affinity values lower than those measured for human hemoglobin in the presence of 2,3-DPG. The interaction of bovine hemoglobin with anions is modulated by the hydrophobic characteristics of the protein. Comparison of the hydropathy plots of primate and ruminant hemoglobins indicates constant regions of opposite hydrophobicity, which have fixed amino acid differences. A model is proposed for explaining the regulation of oxygen affinity by chlorides, as an alternative to the classic modulation by 2,3-DPG.