The labilization of hemoglobin by cobalt. Its effect on globin synthesis in reticulocytes.

Abstract

To elucidate a mechanism for cobalt‐stimulated globin synthesis in rabbit reticulocytes, the cells were incubated with 1 mM CoCl2 containing 60Co. Although the cells incorporated cobalt irreversibly, evidence for the synthesis of cobalt‐protoporphyrin was not obtained. More than 90% of the cobalt recovered in the cell cytoplasma was bound to the globin moiety of hemoglobin. Similar results were obtained with erythrocytes and purified hemoglobin incubated with 60CoCl2.By CM‐Sephadex chromatography and isoelectric focusing it was found that cobalt‐labelled hemoglobin differs slightly in charge from native hemoglobin, possessing a lower isoelectric point.It was also demonstrated that the heme in cobalt‐labelled hemoglobin is less firmly bound to globin than the heme in the native protein, and that the purified cobalt‐treated protein can stimulate globin synthesis in rabbit reticulocytes.It is postulated that in reticulocytes cobalt stimulates globin synthesis indirectly by labilizing intracellular hemoglobin.