This is the first time that anyone has created a completely autonomous organism that uses 21 amino acids and has the metabolic machinery to build those amino acids.
"We now have the opportunity to ask whether a 21-amino acid form of life has an evolutionary advantage over life with 20 amino acids," says the report's lead author Peter Schultz, Ph.D., TSRI professor of chemistry and Scripps Family Chair of TSRI's Skaggs Institute of Chemical Biology.
"We have effectively removed a billion-year constraint on our ability to manipulate the structure and function of proteins," he says.
In addition to demonstrating that life is possible with additional amino acids, the work is of great relevance to science and medicine because it enables scientists to chemically manipulate the proteins that an organism produces within the organism itself. This gives scientists a powerful tool for research, from determining molecular structures to creating molecular medicines.
Why Expand the Genetic Code?
Life as we know it is composed, at the molecular level, of the same basic building blocks for instance, all life forms on Earth use the same four nucleotides to make DNA. And almost without exception, all known forms of life use the same common 20 amino acids--and only those 20--to make proteins.
"The question is," asks Schultz, "why did life stop with 20 and why these 20?"
While the answer to that question may be elusive, the 20-amino acid barrier is far from absolute. In some rare instances, in fact, certain organisms have evolved the ability to use the unusual amino acids selenocysteine and pyrrolysine--sli
Contact: Jason Bardi
Scripps Research Institute