Molecular basis of hemoglobin adaptation in the high-flying bar-headed goose
Fig 2
Bar-headed goose evolved an increased Hb-O2 affinity relative to greylag goose and their reconstructed ancestor, AncAnser.
Triangulated comparisons of purified rHbs involved diffusion-chamber measurements of O2-equilibria (A) and stopped-flow measurements of O2 dissociation kinetics (B). O2-affinities (P50, torr; ± 1 SEM) and dissociation rates (koff, M-1s-1; ± 1 SEM) of purified rHbs were measured at pH 7.4, 37° C, in the absence (stripped) and presence of allosteric effectors ([Cl-], 0.1 M; [Hepes], 0.1 M; IHP/Hb tetramer ratio = 2.0; [heme], 0.3 mM in equilibrium experiments; [Cl-], 1.65 mM; [Hepes], 200 mM; IHP/Hb tetramer ratio = 2.0; [heme], 5 μM in kinetic experiments). Letters distinguish measured values that are significantly different (P<0.05).