Scientists Produce First
Organism Able to Synthesize
Additional Amino Acid
Betterhumans Staff
[Monday, January 13, 2003] Scientists have created a strain of
bacteria able to synthesize 21 amino acids -- one more than the 20
that every natural living thing on Earth has used to date for protein
construction.
Scheduled for publication in the January 29 edition of the Journal
of the American Chemical Society, the research is a step towards
testing whether 20 is a magic number or whether additional amino
acids can confer evolutionary advantages.
"Why did life settle on 20 amino acids?" asks Ryan Mehl, a
researcher with Franklin & Marshall College in Lancaster,
Pennsylvania who worked on the study. "Would more amino acids
give you a better organism -- one that could more effectively
adapt if placed under selective pressure?"
Creating new life
Mehl and a team led by Peter Schultz from the Scripps Research
Institute in La Jolla, California created their novel organism by
altering E. coli bacteria so that they produced the new amino acid
p-aminophenylalanine.
They did this by converting a stop codon, genetic code that
usually blocks protein synthesis, to a string that codes for p-
aminophenylalanine.
Analysis of proteins showed that the experiment worked. "This
bug is self-sufficient; it can make, load and incorporate the new
amino acid in the emerging protein all on its own," Mehl says. "It's
a bona fide unnatural organism now."
Benefits of more amino acids
To determine the benefits of additional amino acids, the
researchers plan to expose both their novel bacteria and
unmodified bacteria to selective pressures and compare their
development.
They are also looking to create organisms able to synthesize
amino acids that could be useful for producing such things as
pharmaceuticals.
In the meantime, to prevent their bacteria from existing outside
the lab they have shut off its ability to synthesize one of the
original 20 amino acids, leucine.
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