Characterization of activin A binding sites on the human leukemia cell line K562

Recombinant activin A was radioiodinated to a high specific activity with maintenance of bioactivity using the Bolton-Hunter method. The human leukemia cell line K562, known to differentiate in response to activin A, was found to possess high affinity [125I]BH-activin A receptors (Kd approximately 0.13 nM) with a low number of receptors per cell (approximately 600 per cell). This receptor was found to be specific as FSH, LH, GnRH, and TGF-beta 1 do not compete for binding. This is the first description of binding sites for this protein hormone on K562 cells.