Mammalian epidermal protein synthesis: initiation factors

There is a deficiency of initiation in protein-synthesizing systems prepared from mammalian epidermis. These systems do not respond to inhibitors of initiation although they remain sensitive to elongation inhibitors and exogenous ribonuclease. In spite of this deficiency of initiation, active protein factors which support initiation reactions are present in the potassium chloride extract of mammalian epidermal ribosomes. A factor corresponding to the reticulocyte factor IF-MP has been isolated. An inhibitor of initiation is also present in the epidermal KCl wash.