Differences in affinity of variant beta chains for alpha chains: a possible explanation for the variation in the percentages of beta chain variants in heterozygotes.

The alpha and beta chains of the hemoglobins A, S, Leslie and N-Baltimore have been isolated as PMB derivates by CM-cellulose and DEAE-cellulose chromatography. The relative affinities of the betaA, betaS, betaLeslie and betaN-Baltimore chains for alpha chains were measured through quantitation by chromatography of the hemoglobins A and Leslie, A and S, and A and N-Baltimore that were formed when variable amounts of alpha chains were added to a mixture of equal amounts of the appropriate beta chains. The data indicate a greatly decreased affinity of betaLeslie chains for alpha chains; a similar preference of alpha chains for betaA chains was observed for mixtures involving alpha, betaA, and betaS chains, but the affinity of betaS chains for alpha chains was higher than that of betaLeslie chains. The betaN-Baltimore chains assembled with alpha chains at a similar rate as betaA chains. The data as interpreted indicate that the affinity of certain beta chains for alpha chains can be a major post-translational control mechanism which regulates the level of a beta chain variant in heterozygotes.