Metal substitutions at the Diiron site of hemerythrin. A dicobalt(II) derivative

The invertebrate O 2 -carrying protein hemerythrin contains a nonheme diiron active site. A simple method is described for high-yield preparation of hemerythrin in which cobalt is substituted for the nonheme iron. The cobalt-substituted hemerythrin contains nearly the same polypeptide helix content as the native protein and, like the native protein, is octameric, indicating that the protein subunit structure and intersubunit interactions have been preserved. Close to 2 Co/Hr subunit with no detectable iron is reproducibly obtained, suggesting that cobalt occupies the same coordination sites as iron inthe native protein