Effect of carboxyterminal modification on the oligomeric structure of human beta hemoglobin

A broad beta chain band region containing multiple components was observed with both native beta and Des(His-146, Tyr-145) beta chains following isoelectric focusing on agarose gels (pH 6.0-8.0). In contrast to the tetramer-monomer system of beta chains, a distinct separation of three components (tetramer, dimer and monomer) was seen for Des(His-146, Tyr-145) beta chains indicative of an oligomeric structural beta model with a stable dimer species. Protein dilution (500 to 15.6 microM in heme) amplified the more cathodic (presumably dimeric and monomeric) components of these chains, and titration with partner alpha chains resulted in a selective depletion of the monomer (most cathodic) component which could be quantitatively correlated with assembly of the hemoglobin tetramer.