Direct incorporation of hydroxyproline into protein of sycamore cells incubated at growth-inhibitory levels of hydroxyproline.

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Abstract
The fact that [alpha][alpha][image]-dipyridyl totally inhibited proline hydroxylation in sycamore cells made it possible to demonstrate direct incorporation of hydroxyproline into protein of sycamore cells exposed to a growth-inhibitory concentration of hydroxyproline (0. 2 mM). Hydroxyproline was not incorporated when present at a noninhibitory concentration (0. 007 mM); the evidence indicates that the hydroxyproline found in protein under these conditions was incorporated as proline and subsequently hydroxylated. When hydroxyproline inhibited the growth of sycamore cells, there was no decrease in the incorporation of proline, nor was there any change in the extent of proline hydroxylation over the period studied. Thus growth inhibition probably stems from the incorporation of hydroxyproline into proteins which are thereby rendered nonfunctional.