Puromycin is a powerful inhibitor of protein synthesis. It is an analog of the 3’ end of aminoacyl tRNA. When puromycin is added to a cell-free system containing all the necessary machinery for protein synthesis, incomplete polypeptide chains are released from ribosomes. Each such chain has py y uromycin covalently attached to one end.

a) Explain these results.

b) To which end of the polypeptide chains would you expect the puromycin to be bound? Explain fully.

c) Would you expect puromycin to bind to the A or P site on the ribosome, or to both? Explain fully.