The limiting factors of a cell-free system from @entity35 brain for incorporating @entity1522 into protein were studied. The initial more rapid incorporation by microsomes, as opposed to that by ribosomes, is suggested to be due to damage of the ribosomes by detergent. The defect is rectifiable by incubation of the ribosomes in cell sap, so that ribosomes eventually incorporate more @entity535 than do microsomes. This may be because ribonuclease, which is associated with the microsomes but removed by detergent treatment, inactivates the microsomal system. The factor that causes incorporation by microsomes to cease abruptly within 1h is not the lack of any precursor or of @entity855 , of the inactivation of cell-sap factors or the accumulation of inhibitory substances, but is a deficiency of usable messenger ribonucleic acid. Chain initiation in the system is negligible. Ribosomes also become jammed at the end of messenger @entity10731 molecules, unable to terminate protein chains. This eventually leads to jammed polyribosomes, which can be partially relieved by very low concentrations of @entity5808 . A study of the release of polypeptides synthesized in response to the addition of synthetic messengers did not provide any conclusive information on chain-termination sequences, but did indicate some phenomena that were artifacts. It is concluded that ribonuclease action is sufficient to account for all the @entity262 , but a lack of chain initiation may be a contributory factor.

The limiting factors of a cell-free protein-synthesizing system from XXXX brain.

@entity5808 :: ('MESH:D011691', 'Chemical') :: ['puromycin'] @entity1522 :: ('CHEBI:33709', 'Chemical') :: ['amino acids'] @entity535 :: ('CHEBI:33704', 'Chemical') :: ['amino acid'] @entity262 :: ('MESH:D034721', 'Disease') :: ['deficiencies of the cell-free system'] @entity10731 :: ('CHEBI:33697', 'Chemical') :: ['ribonucleic acid'] @entity35 :: ('10116', 'Species') :: ['rat'] @entity855 :: ('MESH:D000255', 'Chemical') :: ['adenosine triphosphate']
@entity35 :: (10116,Species) :: ['rat']
