Now they have capped that discovery with news that they have successfully synthesized the amino acid itself L-pyrrolysine and shown that bacteria can incorporate it into new proteins the biological components which do most of the work in cells.

The importance of their work is the explanation of exactly how the 22nd amino acid is incorporated into proteins inside living cells. The genetic instructions to put pyrrolysine into proteins follows a traditional path that many scientists had not predicted.

For decades following the discovery of the structure of DNA, the dogma was that the genes in the DNA were decoded to produce proteins built from only 20 "canonical" amino acids.

But in 1986, researchers discovered that a 21st amino acid selenocysteine was incorporated into certain proteins. What separated selenocysteine from the other previously identified amino acids was the fact that it was inserted into protein by a very different path.

Each of the canonical amino acids uses a specialized translator protein to decode genetic information as that amino acid. But selenocysteine lacked its own translator protein and is put into the protein through a more circuitous route.

That left open the question of whether future amino acids would follow the traditional path of the first 20 amino acids or the unusual route taken by 21st.

In the end, tradition won out.

The results are described in two papers published in scientific journals this month. The first appeared in the British journal Nature and the second in the journal Chemistry and Biology.

"In recent years, researchers learned to artificially modify a set of translator enzymes so that new amino acids can be genetically programmed in cells to produce novel proteins for biotechnolo
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Contact: Joseph A. Krzycki
Krzycki.1@osu.edu
614-292-1578
Ohio State University
17-Sep-2004