Variation in and Oxygen-Binding Properties of Daphnia magna Hemoglobin

Abstract

The oxygen-binding and molecular properties of hemoglobin from Daphnia magna were investigated. There were negative correlation between p 50 value and hemoglobin concentration in hemolymph. The p 50 values ranged from 5.3 to 1.1 Torr and the n values from 1.2 to 1.6 in 0.1 M phosphate buffer of pH 7.2 at 20 C. The purified hemoglobin solution was separated into at least six components in isoelectric focusing. Hemoglobin solution from animals of different hemoglobin concentration had different proportion of the hemoglobin components, and the increase in oxygen affinity was concomitant with increase in relative amount of hemoglobin components of high pI values. These results indicate that Daphnia magna may become acclimated to various oxygen environments through adjustment of the proportions of hemoglobin components differing in affinity and subunit cooperation.