The findings are scheduled to appear in the Jan. 29 print edition of the Journal of the American Chemical Society, a peer-reviewed journal of the world's largest scientific society. The article was initially published Jan. 4 on the journal's Web site.
The project could eventually give concrete answers to questions that have generally been regarded as purely speculative: Is 20 the ideal number of basic building blocks? Would additional amino acids lead to organisms with enhanced function? Why has the genetic code not evolved further?
"Why did life settle on 20 amino acids?" asks Ryan Mehl, Ph.D., previously a researcher at the Scripps Research Institute in La Jolla, Calif., and now on the faculty of Franklin & Marshall College in Lancaster, Pa. "Would more amino acids give you a better organism -- one that could more effectively adapt if placed under selective pressure?"
To address this question, Mehl and a team of scientists led by Peter Schultz, Ph.D., professor of chemistry at Scripps, added a pathway to an E. coli bacterium that allows it to make a new amino acid -- p-aminophenylalanine (pAF) -- from simple carbon sources. Analytical techniques showed that pAF was incorporated into proteins with a fidelity rivaling that of the 20 natural amino acids.
"This allows you to have a totally autonomous organism that you can 'race'in one pot by evolving the new bacterium alongside its ancestors with 20 amino acids," says Christopher Anderson, a researcher at Scripps and another author
Contact: Beverly Hassell
American Chemical Society