Interaction between alpha 1 and beta 1 subunits of human hemoglobin

We prepared normal and modified alpha and beta globulin chains in which C-terminal residues were enzymatically removed. The CD spectra of the deoxy form of these chains and the reconstituted modified Hb's were measured in the Soret region. The CD spectra of the modified Hb's were markedly different from the arithmetic means of respective spectra of their constituent chains. This difference was ascribed to the interaction between alpha 1 and beta 1 subunits to make the alpha 1 beta 1 dimer. The peak wavelength of the difference CD spectra could be classified into two groups, one was 433 +/- 1 nm and the other 437 +/- 1 nm. A comparison of this classification with the previously identified quaternary structures revealed that the R and T structures showed a maximum of the difference CD spectra at 437 +/- 1 nm and 433 +/- 1 nm, respectively. These results indicated that the R and T structures differed in the interaction between alpha 1 and beta 1 subunits.