Physiologists Discover New Code That Impacts All Biology; Choice Among Synonymous “Fast” Preferred Codons and “Slow” Non-Preferred Codons Regulates Speed of Protein Elongation, Which Influences Protein Folding, Which Determines Function

University of Texas (UT) Southwestern physiologists, trying to understand the genetic code, have discovered a previously unknown code that helps explain which protein should be created to form a particular type of cell. The human body is made up of tens of trillions of cells. Each cell contains thousands of proteins, which determine how the cell should form and what functions it needs to perform. Proteins, in turn, are made up of hundreds of amino acids. The blueprint for each protein is specified by genetic codons, which are triplets of nucleotides that can code for 20 different types of amino acids. The way in which amino acids are linked together then determines which proteins are eventually produced, and in turn, what functions the cell will have. What researchers found was that, not only does the sequence of the amino acids matter, but so does the speed of the process in which the amino acids are put together into a functional protein. “Our results uncovered a new ‘code’ within the genetic code. We feel this is quite important, as the finding uncovers an important regulatory process that impacts all biology,” said Dr. Yi Liu, Professor of Physiology. It was long known that almost every amino acid can be encoded by multiple synonymous codons and that every organism, from humans to fungi, has a preference for certain codons. The researchers found that more frequently used codons − the “preferred codons” − speed up the process of producing an amino acid chain, while less frequently produced codons slow the process. The use of either preferred or non-preferred codons is like having speed signs on the protein production highway: some segments need to be made quickly and others slowly. “The genetic code of nucleic acids is central to life, as it specifies the amino acid sequences of proteins,” said Dr. Liu, the Louise W.
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