CARTER TRIPLETY CODE

Transfer RNAs coupled to amino acids can thus read any genetic sequence, assuring that the amino acids at the other end of the tRNAs assemble together to make the correct sentence in the protein language. The essence of molecular biology, worked out in the 1960s, is that the cell uses the same “base pairing” that also maintains accurate gene copying to decide which tRNA adaptors match successive words in a gene. Each word has a unique partner among the other 63 words. The nanomachines that do the translating, called aminoacyl-tRNA synthetases (aaRS), add a specific amino acid protein letter to adaptor molecules – transfer RNAs or tRNAs – that also contain one of the 64 words of the genetic language. This conversion from a 4-base alphabet into a 20-amino acid alphabet is called translation. The sublime mystery in genetic coding is that twenty of a cell’s genes, these “sentences” composed from these base-triplet words, are actually blueprints for the twenty “nanomachines” – one for each amino acid – that convert those base-triplet words into the twenty-letter alphabet of proteins that make up the rest of life’s machinery. Charles Carter, PhD, and colleagues are attempting to experimentally answer a classic “chicken or the egg” biochemical question about the dawn of life on Earth. Blueprints for living things are written in an organism’s genes using these coded words. Each possible combination of three bases chosen from the A,C,G,T chemical alphabet forms one of 64 unique “words”. In the genetic coding table, each block of three nucleotides is a triplet that represents a single amino acid. “Genetic coding” is the term used to describe how the four bases of DNA – the A, C, G, and Ts –are strung together so that cellular machinery, especially the ribosome, can interpret genetic instructions and convert sequences of nucleotide bases in genes into sequences of amino acids in proteins. Sloan Foundation has awarded Charlie Carter, PhD, a professor in the UNC Department of Biochemistry and Biophysics at the UNC School of Medicine, a $1.5-million grant to try to answer that vexing question in collaboration with Peter Wills, PhD, at the University of Auckland, New Zealand, and Milena Popovic, PhD, and Mark Ditzler, PhD in the Center for the Emergence of Life at NASA Ames Research Center. How did random chemicals wind up embedding functionality into genes? Answers to that question reside in evolutionary molecular biology.

CARTER TRIPLETY CODE

That “chicken-and-egg-question” – how do you get a code when you need one to make one? – is the quintessential challenge posed by the origin of life on Earth. But nearly 4 billion years later, it remains deeply mysterious how nature learned to use symbolic coding relationships to interpret genes, especially those that now enforce the coding rules inside every living cell. One of nature’s most ingenious inventions, the genetic code, unlocked a vast new world of molecular machinery that allowed the first independently living cells to emerge from the complex chemistry that existed on Earth before the origin of life.

Sloan Foundation has awarded $1.5 million to Charles Carter, PhD, at the UNC School of Medicine, who will lead lab experiments showing how critical molecules precisely interacted, evolved together, and led to life on Earth billions of years ago.

Carter triplety