Hemoglobin Einstein: Semisynthetic deletion in the B‐helix of the α‐chain

The influence of the deletion of the tetra peptide segment α 23–26 of the B‐helix of the α‐chain of hemoglobin‐A on its assembly, structure, and functional properties has been investigated. The hemoglobin with the deletion, ss‐Hemoglobin‐Einstein, is readily assembled from semisynthetic α 1–141 des 23–26 globin and human β A ‐chain. The deletion of α 23–26 modulates the O 2 affinity of hemoglobin in a buffer/allosteric effector specific fashion, but has little influence on the Bohr effect. The deletion has no influence on the thermodynamic stability of the α 1 β 1 and the α 1 β 2 interface. The semisynthetic hemoglobin exhibits normal intersubunit interactions at the α 1 β 1 and α 1 β 2 interfaces as reflected by 1 H‐NMR spectroscopy. Molecular modeling studies of ss‐Hemoglobin‐Einstein suggest that the segment α 28–35 is in a helical conformation, while the segment α 19–22 is the nonhelical AB region. The shortened B‐helix conserves the interactions of α 1 β 1 interface. The results demonstrate a high degree of plasticity in the hemoglobin structure that accommodates the deletion of α 23–26 without perturbing its overall global conformation.