Excerpt from news.bioscholar.com

A study has shown for the first that the building blocks of proteins can be assembled without instructions from DNA or messenger RNA (mRNA).

A protein, Rqc2, was found playing a role to that of mRNA and specifying which amino acids, the building blocks of proteins, to be in cell mechanism.

“In this , we have a protein playing a role normally by mRNA,” said Adam Frost, assistant professor at University of California, San Francisco.

“This surprising discovery reflects how incomplete our understanding of biology is,” said first author Peter Shen, a postdoctoral fellow in biochemistry at the University of in the US.

The researchers added that the findings have implications for new therapies to treat neurodegenerative diseases such as Alzheimer’s, Amyotrophic lateral sclerosis (ALS) or Huntington’s.

The researchers described that ribosomes are machines on a protein assembly line, linking together amino acids in an order specified by the genetic code.

RCQ protein
A new finding goes against dogma, for the first time that the building blocks of a protein, called amino acids, can be assembled by another protein, and without genetic instructions). The Rqc2 protein (yellow) binds tRNAs (dark blue, teal) which add amino acids (bright spot in middle) to a partially made protein (green). The complex binds the ribosome (white). Image Credit: Janet Iwasa, Ph.D., University of Utah

When something goes wrong, the ribosome is generally disassembled, the blueprint is discarded and the partly made protein is recycled.

The new study, however, that before the incomplete protein is recycled, Rqc2 can prompt the ribosomes to add just two amino acids (of a total of 20) – alanine and threonine – over and over, and in any order.

The nonsensical sequence likely serves specific purposes. The code could signal that the partial protein must be destroyed, or it could be part of a test to see whether the ribosome is working properly, the researchers noted.

For the study, they fine- a technique called cryo-electron microscopy to flash freeze, and then visualse, the quality control machinery in in action.

The findings appeared in the journal Science.