Codon reassignment in the Escherichia coli genetic code.
Most organisms, from Escherichia coli to humans, use the 'universal' genetic code, which have been unchanged or 'frozen' for billions of years. It has been argued that codon reassignment causes mistranslation of genetic information, and must be lethal. In this study, we successfully reassigned the UAG triplet from a stop to a sense codon in the E. coli genome, by eliminating the UAG-recognizing release factor, an essential cellular component, from the bacterium. Only a few genetic modifications of E. coli were needed to circumvent the lethality of codon reassignment; erasing all UAG triplets from the genome was unnecessary. Thus, UAG was assigned unambiguously to a natural or non-natural amino acid, according to the specificity of the UAG-decoding tRNA. The result reveals the unexpected flexibility of the genetic code.
Mukai
Takahito
T
RIKEN Systems and Structural Biology Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama 230-0045, Japan.
Hayashi
Akiko
A
Iraha
Fumie
F
Sato
Aya
A
Ohtake
Kazumasa
K
Yokoyama
Shigeyuki
S
Sakamoto
Kensaku
K
D000596:Amino Acids / Q000378:metabolism; D003062:Codon; D018388:Codon, Terminator; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics; D017353:Gene Deletion; D010454:Peptide Termination Factors / Q000235:genetics
D000596:Amino Acids; D003062:Codon; D018388:Codon, Terminator; D029968:Escherichia coli Proteins; D010454:Peptide Termination Factors; C489005:prfA protein, E coli