Bacteria use expanded genetic code

Abstract

The genome of every cell on Earth uses four DNA bases—adenine, thymine, cytosine, and guanine—to encode proteins. Chemists have long dreamed of expanding that set to create cells that work with both natural and unnatural nucleic acids. An expanded collection of bases could allow cells to synthesize unnatural amino acid-containing proteins that have new functions and could be useful as novel drugs, vaccines, and nanomaterials. But the closest researchers had gotten was to translate DNA with expanded base sets into proteins in test tubes. Now, Floyd E. Romesberg of Scripps Research Institute California and coworkers have gone all the way by putting an expanded genetic code into bacteria and getting the microbes to use it to synthesize an unnatural protein (Nature 2017, DOI: 10.1038/nature24659). The researchers got a strain of Escherichia coli to work with dNaM and dTPT3, aromatic DNA bases that pair with each other through complementary packing and