Functional Chloroplast Polyribosomes from Tobacco Leaves

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Science  10 Mar 1967:
Vol. 155, Issue 3767, pp. 1271-1273
DOI: 10.1126/science.155.3767.1271


Incubation of isolated to bacco chloroplasts with ingredients re quired for protein synthesis resulted in liberation of 70S ribosomnes and poly ribosomes that no longer sedimented with the chloroplasts. With increasing time of incubation, polyribosomes broke down to 70S monosomes. Similarly, microgram quantities of ribonuclease caused chloroplast polyribosomes to break down into monosomes. Both polyribosomes and 70S ribosomes that were isolated on sucrose density gra dients and tested separately in cell-free systems were capable of protein syn thesis; however, polyribosomes formed more protein per unit of RNA than monosomes did.

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