Structural study and preliminary crystallographic data for the hemoglobin from reindeer (Rangifer tarandus tarandus)

The ferric form of reindeer hemoglobin (Rangifer tarandus tarandus) has been crystallized in an orthorhombic crystalline form from polyethylene glycol solutions, at pH 8.2. The crystals belong to the orthorhombic space group P2₁2₁2₁, with unit cell edges a = 84.2 A ̊, b = 59.9 A ̊, c = 119.5 A ̊; one hemoglobin tetramer is contained in the asymmetric unit. The crystals diffract X-rays to a limit spacing of 3.0 Å. Inspection of amino acid sequences in the N-terminal region of β-chains, and analysis of hemoglobin three-dimensional models, allows one to rationalize, on a molecular basis, the reduced O₂ affinity and the decreased effect of organic phosphates observed in ruminant hemoglobins. By analogy, the analysis is extended to birds and reptiles, whose hemoglobin β-chains display, as in ruminants, the deletion of the N-terminal residue and a methionine at the NA2 position.