Purification and characterization of an iron-binding protein from the blue crab (Callinectes sapidus)

The presence of an iron-binding protein in the hemolymph of the blue crab (Callinectes sapidus) was detected by gel filtration of 59Fe-labeled hemolymph. The iron-binding protein was purified to homogeneity by ion exchange chromatography. 2. This protein has a mol. wt of 155,000 and consists of a single polypeptide chain with an isoelectric point of 5.0. 3. Analysis of the iron-loaded protein indicates that it has a high affinity for iron and the capacity to bind approximately 10 atoms iron/molecule protein. 4. The isolation of a specific iron-binding protein from the blue crab (Callinectes sapidus) provides additional support for the proposal that such proteins are an ancient evolutionary development not necessarily linked to the appearance of iron proteins (hemoglobin and hemerythrin) as a means for oxygen transport.