The structure of hemoglobin reconstituted with deuteroheme

The structure of horse methemoglobin reconstituted with deuteroheme, in which the heme vinyl substituents are replaced by hydrogens, has been compared with that of native horse methemoglobin by X-ray difference Fourier techniques. The tertiary structures of the two molecules are almost completely identical, with the exception of small perturbations in the globin which occur in direct response to the missing vinyls. These perturbations are, however, highly localized and do not propagate beyond the immediate vicinity of the hemes. Contrary to expectation, complete removal of these heme vinyls results in much less drastic structural changes than does replacement by ethyl substituents, as in methemoglobin reconstituted with mesoheme.