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. 1994 Jan 1;13(1):249-57.
doi: 10.1002/j.1460-2075.1994.tb06255.x.

The second to last amino acid in the nascent peptide as a codon context determinant

S Mottagui-Tabar  1 , A Björnsson, L A Isaksson
Affiliations

The second to last amino acid in the nascent peptide as a codon context determinant

S Mottagui-Tabar et al. EMBO J. .

Abstract

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.

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