Genetically crosslinked hemoglobin: a structural study.
The crystal structures of three recombinant human hemoglobins, rHb1. 0, rHb1.1 and rHb1.2, have been determined in the deoxy state at 1.8 A resolution. Two of the three proteins, rHb1.1 and rHb1.2, contain a genetic fusion of the alpha subunits, a one- or two-glycine link, respectively, whereas rHb1.0 does not. The glycine crosslinks, localized between one N- and C--termini pair of the alpha subunits in the deoxy crystalline state, do not perturb the overall tertiary or quaternary or even the local structure of hemoglobin. Therefore, genetic fusion to prevent the dissociation of the hemoglobin tetramer, thereby inhibiting renal clearance based upon molecular size, is a structurally conservative method to stabilize hemoglobin for use as an oxygen-delivery therapeutic.