Xenopus laevis hemoglobin and its hybrids with hemoglobin A+.

Isolated α and βchains from Xenopus laevis hemoglobin have been purified. The isolation procedure yields native α chains whose functional behavior has been characterized and compared with that of human α chains. Isolated β chains in the presence of oxygen are characterized by low stability, and hence their functional characterization was limited to the CO binding kinetics. When stoichiometric amounts of the isolated α and β chains are mixed, a tetramer characterized by heme-heme interactions and oxygen affinity comparable to that of the native molecule is readily reconstituted. Moreover, both chains, under appropriate conditions, form stable hybrid tetramers with the partner subunits from human hemoglobin; results on the functional properties of these hybrid hemoglobins are presented and discussed in relation to the stereochemical model of the Root effect.