Amino Acids of a Protein Can Assemble Without DNA and mRNA Blueprints

There may just be a new role for proteins. Scientists have found for the first time that the building blocks of a protein, called amino acids, can be assembled without blueprints--DNA and an intermediate template called messenger RNA (mRNA).

"This surprising discovery reflects how incomplete our understanding of biology is," said Peter Shen, first author of the new study, in a news release. "Nature is capable of more than we realize."

Think of the cell as a well-run factory. Ribosomes are machines on a protein assembly line, linking together amino acids in an order specified by the genetic code. When something goes wrong, the ribosome can stall, and a quality control crew is summoned to the site. The ribosome is then disassembled, the blueprint discarded and the partly made protein is recycled.

In this latest study, though, the researchers discovered a surprising role for one member of the quality control team: a protein named Rqc2. Before the incomplete protein is recycled, Rqc2 prompts the ribosomes to add just two amino acids, alanine and threonine, over and over and in any order. In other words, the auto assembly line keeps on going despite having lost its instructions.

"In this case, we have a protein playing a role normally filled by mRNA," said Adam Frost, one of the researchers. "I love this story because it blurs the lines of what we thought proteins could do."

The findings reveal a bit more about proteins. There are also many interesting implications, and the researchers plan to now determine when and where this process happens, and what happens when it fails.

The findings are published in the journal Science.

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