Graphic method for determination of allosteric constants

Abstract The maximum slope of the plot, appearing in the paper of Watari & Isogai (1976) , was derived algebraically as a function of allosteric constants c and α m or β m (= cα m ), and the relation between L , c , and α m or β m , was also obtained, where L = T o R o , c = K R K T , α m = F m K R , β m = F m K T , R o and T o are concentrations of unligated R and T states respectively, K R and K T are microscopic dissociation constants, and F m is the ligand concentration at the maximum slope of the plot. When the maximum slope is increased by one, the value becomes Hill constant, n . Nomographs which enable easier estimation of allosteric constants, L and c , were constructed from the two given values, the maximum slope of the plot, n − 1, and α m or β m , in the cases where the maximum number of ligands, N , was 2 and 4. In the nomograph, log c is plotted against log L 2 c N keeping the value of the maximum slope of the plot and that of α m or β m constant. These nomographs show that the representation is symmetrical in the cases of L 2 c N > 1 and L 2 c N