New Amino Acid Discovered

EricMargel writes: "As published in Science, researchers at the Ohio State University claim to have discovered the 22nd known amino acid, pyrrolysine, the first discovered since 1986." I hope rice and beans are still sufficient to get all the needed amino acids.

Comments

Creating *new* bases

[HorsePunchKid]

There was an article in Science News a year or so ago that described some research on the topic of making DNA code for new bases. Apparently it's somewhat of a mystery why all life has "chosen" to use the same set of amino acids as a basis. With 64 codons, one would expect to be able to code for 64 different amino acids, but there's some redundancy that allows for some error tolerance. It turns out that there are some branches of life (maybe the Archea or something, I'm not sure anymore) that actually use bases that don't appear in any other organisms. So that spurred researchers to see if they could take some other amino acid that isn't used (something other than the familiar GATC, etc.), and make functional DNA with it. I don't remember exactly how far they got with it, but I believe they essentially had a functioning bacterium. (Whether it could reproduce or not, I'm not sure.)

Ah! Here's the original article: Code Breakers. It's definitely worth a read.

It's not about the amino acid, it's about the tRNA

[ZanshinWedge]

It's very difficult to glean the details of the paper from the abstract alone, but I think I know what's going on. Firstly, this is *not* the first discovery of a non-standard amino acid in nature. There are several rare amino acids that are used by various organisms (usually bacteria) that are not in the "official" registrar of 21 AAs. However, in those cases the amino acid is simply a stand in replacement for a very similar amino acid. Essentially the only thing that need to be changed in that case is the enzyme that produces the amino acid.

This case is special not because of the use of a non-standard amino acid, but because it is an *additional* amino acid rather than a replacement. This means that the machinery of translation of an RNA codon to an amino acid (via tRNA) and the construction of the amino acid (via an enzyme) exists in parallel with the machinery for all the other existing amino acids. This is remarkably interesting because it represents a much larger genetic difference in the amino acid translating machinery, and a difference which we have never seen before.