HEMOGLOBIN ROANNE-[ALPHA-94(G1)-ASP-]GLU] - A VARIANT OF THE ALPHA-1-BETA-2-INTERFACE WITH AN UNEXPECTED HIGH OXYGEN-AFFINITY

In hemoglobin (Hb) Roanne, the aspartate residue alpha 94(G1) is repla ced by a glutamic acid. This residue plays a key role in the structura l changes affecting the alpha 1 beta 2 contact area during the deoxy- to oxy-state transition in the hemoglobin molecule. Aspartate alpha 94 (G1) is involved in several contacts both in the deoxy- and oxy-struct ures. The most important of those is a hydrogen bond with asparagine b eta 102 (G4), stabilizing the oxygenated structure. Alteration of this contact usually leads to a decrease in oxygen affinity. Hb Roanne is the first example in which an increased oxygen affinity was found as a result of a structural modification at this position. Functional data suggested that the mechanisms responsible for this altered property a re a destabilisation of the T-structure and a modification of the allo steric equilibrium.