Interactions at the alpha 1 beta 1 interface in hemoglobin: a single amino acid change affects dimer ratio in transgenic mice expressing human hemoglobin.

The erythrocytes of transgenic mice expressing human hemoglobin contain mouse, human, and two hybrid hemoglobins. These hybrids include a predominant one, the human-alpha/mouse-beta and one found at lower levels, the human-beta/mouse-alpha. We used molecular modeling-aided hydropathic analysis of the globin alpha 1 beta 1 interface to identify a residue partly or wholly responsible for this distribution. Hemoglobin containing a single amino acid change [beta 112(G14)Cys-->Val] was expressed in transgenic mice. The hybrid ratio was reversed in transgenic mice expressing this mutated human hemoglobin as compared to the control transgenic mice expressing native human hemoglobin. These results demonstrate the importance of subunit assembly in the expression of hybrids in transgenic animals and may lead to successful design approaches for optimal expression of hemoglobin in larger animals such as the pig.