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Transfer RNA-Dependent Amino Acid Biosynthesis: An Essential Route to Asparagine Formation
Bokkee Min, Joanne T. Pelaschier, David E. Graham, Debra Tumbula-Hansen and Dieter Söll
Proceedings of the National Academy of Sciences of the United States of America
Vol. 99, No. 5 (Mar. 5, 2002), pp. 2678-2683
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/3058008
Page Count: 6
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Biochemical experiments and genomic sequence analysis showed that Deinococcus radiodurans and Thermus thermophilus do not possess asparagine synthetase (encoded by asnA or asnB), the enzyme forming asparagine from aspartate. Instead these organisms derive asparagine from asparaginyl-tRNA, which is made from aspartate in the tRNA-dependent transamidation pathway [Becker, H. D. & Kern, D. (1998) Proc. Natl. Acad. Sci. USA 95, 12832-12837; and Curnow, A. W., Tumbula, D. L., Pelaschier, J. T., Min, B. & Söll, D. (1998) Proc. Natl. Acad. Sci. USA 95, 12838-12843]. A genetic knockout disrupting this pathway deprives D. radiodurans of the ability to synthesize asparagine and confers asparagine auxotrophy. The organism's capacity to make asparagine could be restored by transformation with Escherichia coli asnB. This result demonstrates that in Deinococcus, the only route to asparagine is via asparaginyl-tRNA. Analysis of the completed genomes of many bacteria reveal that, barring the existence of an unknown pathway of asparagine biosynthesis, a wide spectrum of bacteria rely on the tRNA-dependent transamidation pathway as the sole route to asparagine.
Proceedings of the National Academy of Sciences of the United States of America © 2002 National Academy of Sciences