The second to last amino acid in the nascent peptide as a codon context determinant.
Forty-two different sense codons, coding for all 20 amino acids, were placed at the ribosomal E site location, two codons upstream of a UGA or UAG codon. The influence of these variable codons on readthrough of the stop codons was measured in Escherichia coli. A 30-fold difference in readthrough of the UGA codon was observed. Readthrough is not related to any property of the upstream codon, its cognate tRNA or the nature of its codon-anticodon interaction. Instead, it is the amino acid corresponding to the second upstream codon, in particular the acidic/basic property of this amino acid, which seems to be a major determinant. This amino acid effect is influenced by the identity of the A site stop codon and the efficiency of its decoding tRNA, which suggests a correlation with ribosomal pausing. The magnitude of the amino acid effect is in some cases different when UGA is decoded by a wildtype form of tRNA(Trp) as compared with a suppressor form of the same tRNA. This indicates that the structure of the A site decoding tRNA is also a determinant for the amino acid effect.
Mottagui-Tabar
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S
Department of Microbiology, Stockholm University, Sweden.
Björnsson
A
A
Isaksson
L A
LA
D000596:Amino Acids / Q000737:chemistry / Q000235:genetics*; D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism; D001483:Base Sequence; D003062:Codon; D004247:DNA; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli; D007526:Isoelectric Point; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000235:genetics*; D014176:Protein Biosynthesis; D012343:RNA, Transfer / Q000235:genetics; D012270:Ribosomes / Q000378:metabolism
D000596:Amino Acids; D003062:Codon; D010455:Peptides; D004247:DNA; D012343:RNA, Transfer; D000604:Amino Acyl-tRNA Synthetases