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Abstract
Cell-free incorporation of amino acid into paramecium protein was accomplished by using ribosomes, soluble fraction, guanosine triphosphate and adenosine triphosphate. Less than 20% of the incorporated label was detected in the soluble fraction, indicating that little if any complete de novo synthesis occurred. Incorporation was markedly decreased by submicrogram concentrations of RNase and by decreasing [Mg2+] to below 3 μmoles/ ml. A ‘pH 5 fraction’ from mouse liver was able to replace the paramecium soluble fraction but attempts to obtain active ‘pH 5 fractions’ from paramecium failed. Evidence is presented for the presence of polyribosomes in paramecium; there was some indication that they were active in amino acid incorporation. Following incorporation, 80s ribosomes labelled with amino acid were recovered; subjecting these to Mg2+-deficient buffer caused dissociation into 45s and 30s units. A considerable portion of the label remained with the heavier unit.
- Accepted:
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