Reciprocal effects in human hemoglobin: direct measurement of the dimer-tetramer association constant at partial oxygen saturation.
An equilibrium gel permeation technique has been developed for determining as a function of oxygenation state the equilibrium constants for association of hemoglobin subunits. By using this method, the dimer-tetramer constant for human hemoglobin at a partial oxygenation state corresponding to 20% saturation for tetramers has been determined as 3.7 X 10(6) M-1 (dimers). Under the same conditions the corresponding constant for fully oxygenated hemoglobin is 4.1 X 10(5) M-1. These results are found to be in good agreement with the predicted behavior of the association reaction based upon oxygen binding curves measured as a function of protein concentration. Thus a high degree of consistency is found between the two independent experimental approaches to the reciprocal effects of this linkage system, lending support to the theory proposed earlier for these phenomena.
D006454:Hemoglobins; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D010100:Oxygen / Q000097:blood; D010108:Oxyhemoglobins; D013053:Spectrophotometry / Q000379:methods
D006454:Hemoglobins; D046911:Macromolecular Substances; D010108:Oxyhemoglobins; D010100:Oxygen