Abstract
Oxygen equilibria were measured on a number of human hemoglobins, which had been "stripped" of organic phosphates and isolated by column chromatography. In the presence of 2 x 10(-4) M 2,3-diphosphoglycerate (2,3-DPG), the P(50) of hemoglobins A, A(2), S, and C increased about twofold, signifying a substantial and equal decrease in oxygen affinity. Furthermore, hemoglobins Chesapeake and M(Milwaukee-1) which have intrinsically high and low oxygen affinities, respectively, also showed a twofold increase in P(50) in the presence of 2 x 10(-4) M 2,3-DPG. In comparison to these, hemoglobins A(IC) and F were less reactive with 2,3-DPG while hemoglobin F(I) showed virtually no reactivity. The N-terminal amino of each beta-chain of hemoglobin A(IC) is linked to a hexose. In hemoglobin F(I) the N-terminal amino of each gamma-chain is acetylated. These results suggest that the N-terminal amino groups of the non-alpha-chains are involved in the binding of 2,3-DPG to hemoglobin.