INCORPORATION INTO POLYPEPTIDE AND CHARGING ON TRANSFER RIBONUCLEIC ACID OF AMINO ACID ANALOG 5',5',5',-TRIFLUOROLEUCINE BY LEUCINE AUXOTROPHS OF ESCHERICHIA COLI

Some leucine auxotrophs of Escherichia coli were previously shown to be adaptable to grow on 5′,-5′,5′-trifluoroleucine in a chemostat. In these experiments bacteria naive to trifluoroleucine were tested for their ability to carry out various reactions when confronted with this analog in the absence of leucine. A crude extract of aminoacyl synthetases charged about two to three times as much trifluoroleucine as leucine to transfer ribonucleic acid. The trifluoroleucine charging was inhibited, in decreasing order of effectiveness, by leucine, isoleucine, phenylalanine, and cysteine. Intact cells incorporated trifluoroleucine into polypeptide for about an hour, whereupon incorporation ceased. The initial rate was somewhat greater than the initial rate of leucine incorporation. In vivo incorporation of trifluoroleucine was inhibited by leucine, isoleucine, and phenylalanine. When histidine was used as an indicator of protein synthesis in vivo the ratio of trifluoroleucine to histidine incorporation was about twice the leucine to histidine ratio. The trifluoroleucine to histidine ratio was reduced in the presence of isoleucine or phenylalanine; the leucine to histidine ratio was unaffected. A combination of isoleucine and phenylalanine decreased the trifluoroleucine to histidine ratio below the leucine to histidine ratio. Ribonucleic acid synthesis, as measured by uracil incorporation, was markedly reduced by incubation in trifluoroleucine. Synthesis was fully restored by 1μg/ml of chloramphenicol, an amount too low to relax ribonucleic acid synthesis in the absence of amino acids. © 1969, American Chemical Society. All rights reserved.