Incorporation of unsaturated isoleucine analogues into proteins in vivo

Abstract

The translational activity of various unsaturated analogs of L-isoleucine was evaluated using an Escherichia coli strain auxotrophic for isoleucine. It was observed that the alkene [2-amino-3-methyl-4-pentenoic acid (2)] and alkyne [2-amino-3-rnethyl-4-pentynoic acid (3)] derivatives of L-isoleucine can support protein synthesis at levels approximately 50% of that observed in cultures supplemented with isoleucine. However, no incorporation of the αC or βC methylated derivatives could be detected. In order to examine the stereoselectivity of incorporation, the (2S, 3s) and (2S, 3R) diastereomers of 2 and 3 were prepared. The extents of isoleucine substitution in vivo were 80% and 70% for (2S, 3S)-2 and (2S, 3S)-3, respectively, under the conditions examined in this study.

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