EFFECT OF CARBOXYTERMINAL MODIFICATION ON THE OLIGOMERIC STRUCTURE OFHUMAN BETA-HEMOGLOBIN

A broad beta chain band region containing multiple components was obse rved with both native beta and Des(His-146, Tyr-145)beta chains follow ing isoelectric focusing on agarose gels (pH 6.0-8.0). In contrast to the tetramer-monomer system of beta chains, a distinct separation of t hree 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 mu M in he me) amplified the more cathodic (presumably dimeric and monomeric) com ponents of these chains, and titration with partner a chains resulted in a selective depletion of the monomer (most cathodic) component whic h could be quantitatively correlated with assembly of the hemoglobin t etramer. (C) 1994 Academic Press, Inc.