viernes, 2 de enero de 2015

Science Graphic of the Week: Scientists Discover the First Protein That Can Edit Other Proteins

Janet Iwasa, PH.D., University Of Utah

The most important job inside any cell is making proteins, and they are all made using instructions from DNA. This process is practically gospel in the field of molecular biology, but new research identifies some exceptions. Some proteins, it turns out, can make other proteins.

Proteins are assembled from amino acids inside cellular structures called ribosomes. Normally, the blueprints for every protein—from disease fighting antibodies to structural components that allow muscles to contract—are encoded in DNA and delivered to the ribosomes by molecules called messenger RNA. There, those genetic instructions are used by a related molecule called transfer RNA to build the protein.

The image above, published today in the journal Science shows a totally different way of building a protein. The yellow blob is a protein called Rqc2 that’s doing the job normally done by messenger RNA. It is connected to the transfer RNA (the blue and light green blobs), telling the ribosomes (the mass of white curls) to insert a random sequence of amino acids into the protein string.

This isn’t a case of a protein going rogue. It seems to be part of the recycling process that occurs when there’s a mistake in a protein being built. When an error is introduced, the ribosomes stall and call in a group of quality control proteins, including Rqc2. In observing this process, the researchers saw how Rqc2 links up with the transfer RNA and tells it to insert a random sequence of two amino acids into the chain (out of 20 total amino acids).

The researchers believe that Rqc2’s seemingly aberrant behavior might be an integral part of keeping your body free of faulty proteins.
It’s possible that it is flagging the protein for destruction, or that the string of amino acids could be a test to see if the ribosome is working properly. People with disorders like Alzheimers and Huntingtons diseases have defective quality control processes for their proteins. Understanding the exact conditions where Rqc2 is triggered, and where it fails to trigger, are the next step in this research, and could be important for developing new treatments for neurodegenerative diseases.

By Nick Stockton
01.01.15 |

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