NEWS OF THE WEEK SCIENCE
ural amino acid to the tRNA. The modified bacteria can incorporate />-aminophenylalanine into myoglobin "with fidelity and efficiency rivaling those of the common 20 amino acids," the scien tists note. The bacteria seem to suffer no ill effects from the modifications. To ensure that the modi fied microorganisms would acids into proteins in the labora n't turn into little Frankentory and have found ways to make steins, Schultz and coworkers microorganisms express nonnat disabled them: The altered ural proteins. But the Scripps E. coli can only survive under team's new study is the first in carefully designed lab condi which free-living microorganisms tions and thus can't escape Schultz have been induced to biosyninto the wild. thesize their own nonnatural amino acid and "It's agreat advance," incorporate it into says professor of chem H2N proteins. istry and biochemistry Andrew D. Ellington of To accomplish this, the University of Texas, the researchers added Austin. He notes that t h r e e items to the NH 2 future work in this field bacteria: • Part of a genetic p-Aminophenylalanine will likely focus on the biosynthesis of nonnat pathway from another ural proteins that adopt new func microorganism, which enables tional roles, microorganisms whose the E. coli to biosynthesize/>natural genes mutate to include aminophenylalanine ; stop codons so they can capture • A tRNA that recognizes a biosynthesized nonnatural amino uridine-adenine-guanine (UAG) acids, and organisms that use nonstop codon on mRNA; and natural amino acids throughout • A modified synthetase that their proteomes.—STU B0 RM AN catalyzes addition of the nonnat-
REINVENTING BIOLOGY
Bacteria make protein with nonnatural amino acid they synthesize themselves
T
HE FIRST MICROORGANISMS
that both produce a nonnat ural amino acid and incorpo rate it into proteins have been cre ated by chemistry professor Peter G. Schultz of Scripps Research Institute and coworkers there and at the University of California, Berkeley, and the Genomics In stitute of the Novartis Research Foundation, Lajolla, Calif [J.Am. Chem. Soc, 125,935 (2002)}. The modified Escherichia coli bacteria synthesize proteins us ing a 21st amino acid, ^-aminophenylalanine, in addition to the 20 amino acids common to all other life forms. "We have effec tively removed a billion-year con straint on our ability to manipu late the structure and function of proteins," Schultz says. The additional genes that make this possible are encoded on plasmids, circular pieces of DNAthat the researchers inserted into the bacteria. But Schultz and cowork ers note that the genes could po tentially be incorporated directly in the E. coli genome. Nonnatural proteins produced by modified microorganisms could prove useful as reagents, sen sors, molecular probes, and drugs. Such microorganisms could also be useful for studying fundamen tal evolutionary questions about the number of amino acids used in protein synthesis. "Why did life stop with 20, and why these 20?" Schultz asks. A few natural organ isms do produce unusual amino acids beyond the common 20 (such as selenocysteine and pyrrolysine) and incorporate them in to proteins, but this is rare. In earlier studies, researchers have inserted nonnatural amino HTTP://WWW.CEN-ONLINE.ORG
U N E M P L O Y M E N T
Recession Hits Professionals, College Grads •he employment categories into which chemists tend to fall are being hit par ticularly hard by the current economic slowdown. According to the latest monthly Bureau of Labor Statistics data, the number of unem ployed college graduates has doubled in the past two years. In December 2002, it was 1,120,000, up from 564,000 in December 2000. In contrast, unemployment among those who never went to college rose a relatively more modest 55% over the same period. Unemployment among those with a mana gerial or professional specialty has also dou bled these past two years—to 1,398,000 from 695,000. Overall, the total number of those unem
T!
ployed in all categories jumped 52% between December 2000 and December 2002, to 8.59 million from 5.66 million. The root cause was the sudden end of the spectacular job creation that boosted the num ber of those working from 119 million in De cember 1992 to 136 million in December 2000. These gains dropped the unemployment rate from 7.4% to 4.0%, its lowest level since 1969. The number of those with jobs fell by 2 million during 2001. And in 2002, that num ber failed to post any growth. This all means that, for the past two years, the evolutionary growth in the civilian labor force—which com prises those with a job plus those actively looking for one—has been absorbed by the ranks of the unemployed.-MICHAEL HEYLIN
C & ΕΝ /
JANUARY
?0,
2003
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