Site-directed mutagenesis of the tryptophan residues in yeast eukaryotic initiation factor 4E. Effects on cap binding activity |
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Authors: | M Altmann I Edery H Trachsel N Sonenberg |
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Affiliation: | Department of Biochemistry, McGill University, Montreal, Canada. |
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Abstract: | Initiation factor 4E is a 24-kilodalton polypeptide that binds specifically to the 5' cap structure of eukaryotic mRNAs. Sequence analysis of cDNA clones of initiation factor 4E from several species revealed a high tryptophan content (8 residues). Strikingly, all tryptophans are conserved evolutionarily in number and position between yeast and mammals. Here we show, using site-directed mutagenesis, that two of the tryptophans (those referred to as numbers 1 and 8) are absolutely required for the cap binding activity of an Escherichia coli expressed initiation factor 4E. |
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