Context specific misreading of phenylalanine codons.
It has previously been shown that the phenylalanine codon UUC encoding residue 8 of the Escherichia coli argI gene product, ornithine transcarbamylase, is misread as leucine at a high frequency during phenylalanine starvation. However, no misreading of the UUU encoding residue 3 was observed under these conditions. Using oligonucleotide-directed, site-specific mutagenesis, we have constructed mutants where these codons have been changed. Using these mutant argI genes we see a high level of mistranslation at position 8 during phenylalanine starvation whether the codon is UUU or UUC. With either codon at position 3 we see no leucine substitution. We also constructed a gene with a leucine codon at position 3. The product of this latter mutated gene is stable and active, indicating that preferential turnover of mistranslated protein is not obscuring an otherwise high rate of misreading. This would seem to indicate that it is the context rather than the particular phenylalanine codon which is important in determining these misreading levels.
Precup
J
J
Department of Microbiology, Southern Illinois University, Carbondale 62901.
Ulrich
A K
AK
Roopnarine
O
O
Parker
J
J
D000595:Amino Acid Sequence; D001483:Base Sequence; D003062:Codon; D004926:Escherichia coli / Q000235:genetics*; D008969:Molecular Sequence Data; D009954:Ornithine Carbamoyltransferase / Q000235:genetics; D010649:Phenylalanine / Q000235:genetics*; D010957:Plasmids; D014176:Protein Biosynthesis; D012333:RNA, Messenger; D015183:Restriction Mapping
D003062:Codon; D012333:RNA, Messenger; D010649:Phenylalanine; D009954:Ornithine Carbamoyltransferase