Animal’s Amino Acids Go Unnatural

J. Am. Chem. Soc. 2011

This 1-mm-long worm expresses a red fluorescent protein, suggesting incorporation of tert-butoxycarbonyl lysine (left) or alkynyl lysine.

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Unnatural amino acids, RNA, Caenorhabditis elegans

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Bright Idea Greiss and Chin developed a reporter gene to detect incorporation of unnatural amino acids in a worm. The reporter is a fusion of the genes for green fluorescent protein (GFP) and a red fluorescent protein called mCherry, with a stop codon in the middle, which codes for the unnatural amino acid. If worms are supplied with all of the proper unnatural amino acid incorporation machinery, then they will translate the genes for both fluorophores and will glow at wavelengths that excite both GFP and mCherry. If not, only the GFP gene will be translated. Text in the video indicates which wavelength is currently illuminating the worms.

These worms have successfully incorporated an unnatural amino acid and glow at wavelengths that excite both GFP and mCherry.

J. Am. Chem. Soc. 2011

These worms were not supplied with any unnatural amino acids. As a result, they do not express mCherry and do not glow when illuminated at wavelengths appropriate for mCherry.

J. Am. Chem. Soc. 2011 * Macromedia Flash Player 8 is required to view videos.

For the first time, researchers have incorporated unnatural amino acids into an animal, the nematode worm Caenorhabditis elegans (J. Am. Chem. Soc., DOI: 10.1021/ja2054034). The results could lead to new tools for dissecting the biochemistry of living things. Unnatural amino acids have been placed in bacteria and mammalian cells in several ways. To put the extra amino acids tert-butoxycarbonyl lysine or alkyne-functionalized lysine into worms, postdoc Sebastian Greiss and Jason W. Chin of the Medical Research Council Laboratory of Molecular Biology, in England, turned to established technology—specially designed protein translation machinery from a microbe. They also used mutant worms lacking part of a biochemical surveillance mechanism that would normally destroy unnatural-amino-acid-encoding RNA. The duo confirmed the presence of alkynyl lysine in the worm by selective labeling with biotin azide. They also used a fluorescent reporter that glows red only after successful incorporation. Greiss and Chin say they cannot yet rule out that the worm removes the tert-butoxycarbonyl group from lysine after incorporation. They are producing more protein with the unnatural amino acid so they can determine whether it stays intact.

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ISSN 0009-2347

Copyright © 2011 American Chemical Society