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Protein folding within the cell is influenced by controlled rates of polypeptide elongation
Ist Teil von
Journal of molecular biology, 1992-11, Vol.228 (1), p.7-12
Ort / Verlag
Oxford: Elsevier Ltd
Erscheinungsjahr
1992
Link zum Volltext
Quelle
Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)
Beschreibungen/Notizen
Previous studies have proposed that specific translational pauses have evolved to promote protein folding inside the cell by temporally separating the folding of specific regions of some polypeptide chains during their synthesis. Here we show that this is the case for a bifunctional protein in
Saccharomyces cerevisiae. The yeast
TRP3 gene contains a translational pause comprising ten contiguous non-preferred codons within its second functional domain (indoleglycerol phosphate synthase). Site-directed mutagenesis was used to remove this translational pause by increasing the codon bias of the region without changing the amino acid sequence of the protein (to create the gene
TRP3pr:
pause
replaced). The
TRP3pr gene was able to complement a
trp3 :: URA3 null mutation in yeast. No significant differences in the doubling times of
TRP3 or
TRP3
pr yeast transformants were observed during growth at 25 °C, 30 °C or 37 °C, or in the presence of sublethal concentrations of the analogue, 5-methyltryptophan. However, further analysis of
TRP3 and
TRP3pr transformants revealed that the removal of the translational pause causes a 1.5-fold decrease in indoleglycerol phosphate synthase activity per
TRP3 mRNA. This observation which is statistically significant (
P < 0.05) and reproducible, suggests that translational pausing promotes the correct intracellular folding of the TRP3 protein.