Altmann M, Edery I, Trachsel H, Sonenberg N
Department of Biochemistry, McGill University, Montreal, Canada.
J Biol Chem. 1988 Nov 25;263(33):17229-32.
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.
起始因子4E是一种24千道尔顿的多肽，它能特异性结合真核生物mRNA的5'帽结构。对来自多个物种的起始因子4E的cDNA克隆进行序列分析，发现其色氨酸含量很高（8个残基）。引人注目的是，酵母和哺乳动物之间所有色氨酸在数量和位置上在进化过程中都是保守的。在这里，我们通过定点诱变表明，其中两个色氨酸（即编号为1和8的色氨酸）对于大肠杆菌表达的起始因子4E的帽结合活性是绝对必需的。
