Direct inhibition of the uptake of proline by cycloheximide

Cycloheximinde and puromycin completely inhibited the incorporation of L-proline into acid-insoluble protein by $\text{Achlya. Pfluorophenylalanine}$ did not inhibit net incorporation but halted the synthesis of alkaline phosphatase activity. Of the three inhibitors of protein synthesis tested only cycloheximide immediately and completely interrupted the uptake of proline.