Hemoglobin subunit theta-1, also known as HBQ1, belongs to the Hemoglobin family. Hemoglobin (Hgb) is a 66.7 kDa protein coupled to four iron-binding, methenelinked tetrapyrrole rings (heme). The globin portion of Hgb consists of two alpha chains and two beta chains arranged in pairs forming a tetramer. Each of the four globin chains covalently associates with a heme group. The bonds between alpha and beta chains are weaker than between similar globin chains, thereby forming a cleavage plane that is important for oxygen binding and release. High affinity for oxygen occurs upon relaxation of the alpha1-beta2 cleavage plane. Recombinant human HBQ1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.