Oxygen equilibria and ligand-binding kinetics of erythrocruorins from two burrowing polychaetes of different modes of life, Marphysa sanguinea and Diopatra cuprea

Oxygen equilibria, ligand-binding kinetics and some other physicochemical properties are reported for erythrocruorins of two intertidal polychaetes:Marphysa sanguinea, which inhabits simple, relatively stagnant burrows, and Diopatra cuprea, which inhabits impermeable, parchment-like tubes that are vigorously ventilated. Marphysa erythrocruorin has a higher O2 affinity, which is less pH dependent (at pH 7.3 and 20°C, half-saturation O2 tension, P50, and Bohr factor, φ{symbol}=Δlog P50/ΔpH, are 0.8 mm Hg and -0.25, respectively) than the corresponding parameters (P50=5.5; φ{symbol}=-0.86) in Diopatra (Figs. 1 and 2). In contrast to vertebrate haemoglobins, inorganic salts increase erythrocruorin O2 affinity (Fig. 3). The kinetic rates of ligand binding and dissociation of Marphysa and Diopatra erythrocruorins (Tables 1 and 2) correlate well with the measured O2 affinities and appear to illustrate basic molecular adaptations of the two species to their respective micro-environmental conditions. © 1978 Springer-Verlag.

Duke Scholars

Author Celia J. Bonaventura Marine Science and Conservation