On the Significance of Measurements of Amino Acid Incorporation into the Proteins of Cell-free Preparations.

Abstract

Amino acid incorporation by cell-free extracts of pea seedlings is promoted by adenosine triphosphate and inhibited by adenosine di-phosphate and ribonuclease. These substances have no effect on amino acid incorporation by a mixed bacterial culture. Bacterial incorporation is much more sensitive to antibiotics than incorporation by pea seedling extracts. The kinetics of incorporation and the specific activities of various centrifugal fractions also differ markedly in the two preparations. These facts, plus the observation that pea seedling extracts exhibit the same amount of amino acid incorporation under aseptic conditions, demonstrate that amino acid incorporation by pea seedling extracts is not due to the presence of bacteria in the preparations.