Chemical cross-linking of hemoglobin H. A possible approach to introduce cooperativity and modification of its oxygen transport properties.
Native and reconstituted hemoglobin H molecules were cross-linked with glutaraldehyde at pH values close to the physiological. The Schiff base adducts were analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis before and after reduction with sodium borohydride. The major component had a molecular weight of about 31 000 which corresponded to the dimeric species of the beta subunit. In contrast to the native protein, which has very high oxygen affinity and no heme-heme interaction or 2,3-diphosphoglyceric acid effect, the modified hemoglobin H molecules showed cooperative oxygen binding, decreased oxygen affinity and a noticeable 2,3-diphosphoglyceric acid effect.