1. Polyribosomes have been prepared from the hair follicle tissue of young albino guinea pigs and the yields of especially the larger polyribosomes greatly exceeded those isolated from the same source in earlier studies. 2. These polyribosomes were also highly active in cell-free protein synthesis, being about 700 times more active than those prepared previously. 3. The ribonuclease content of the tissue homogenate preparations from young animals was found to be markedly lower than that obtained from older animals and it was concluded that this lower ribonuclease content was responsible for the improved findings in this work. 4. The properties of the protein synthesis systems established from the guinea pig hair follicle polyribosomes have been investigated using standard techniques. During amino acid incorporation, the polyribosomes degraded by an orderly process of run-off of ribosomes from the mRNA followed by release of the nascent protein chains. Experiments suggested that considerable reinitiation of protein chains occurred during incubation. These and other properties of the cell-free protein synthesis systems are similar to those of other animal systems and thus it is concluded that they are typically of the eukaryote cell-type. © 1971.
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