Polyribosomes of hamster cells: transit time measurements.

The amount of radioactivity incorporated into completed polypeptides and into nascent polypeptides bound to polyribosomes was measured for rapidly dividing, cultured hamster embryo cells incubated in the presence of labelled amino acids. Using a mathematical analysis which took into account variations in the specific activity of the intracellular amino acid pool, these measurements yielded a value for the length of time required for the synthesis of a primary polypeptide of average length, the "transit time." Subject to a number of reasonable assumptions in the mathematical analysis which were, however, only approximately verified, the transit time was found to be 23 +/- 2 sec in four independent experiments. Regardless of the absolute accuracy of this measurement, the method is considered a useful measure of translation independent of transcription.