Reversal of the inhibitory action of the hemin-controlled translational repressor by a post-ribosomal supernatant factor from rabbit reticulocyte lysate.

The inhibitory effect of the hemin-controlled translational repressor (HCR) on protein synthesis by rabbit reticulocyte lysates can be overcome by a factor in the post-ribosomal supernatant fraction. When chromatographed on Sepharose 6B, this supernatant factor migrates as a high molecular weight component that is distinct from the precursor of HCR (prorepressor). The supernatant factor does not appear to act by enzymatically degrading the repressor or by forming a stoichiometric complex with it, but may, rather, replace what has become limiting for protein synthesis due to repressor action.