Platt T, Weber K, Ganem D, Miller J H
Proc Natl Acad Sci U S A. 1972 Apr;69(4):897-901. doi: 10.1073/pnas.69.4.897.
An early, spontaneous amber mutation in the lac i-gene allows translational reinitiation, which results in a mutant lac repressor. Comparison of the amino-terminal sequence of this mutant repressor with the partial amino-acid sequence of the wild-type lac repressor shows that reinitiation occurs at the first internal AUG codon, and results in a mutant protein lacking 42 residues at the amino-terminal end. This protein binds the inducer isopropyl-beta-D-thiogalactoside with normal affinity, and is capable of maintaining a tetrameric structure; however, it does not repress in vivo. These data suggest that the amino-terminal portion of the wild-type lac repressor is necessary either for direct binding to the lac operator or for the correct conformation for binding to DNA.
乳糖抑制基因（lac i -基因）中一个早期自发的琥珀突变允许翻译重新起始，这导致产生一种突变型乳糖阻遏物。将这种突变型阻遏物的氨基末端序列与野生型乳糖阻遏物的部分氨基酸序列进行比较，结果表明重新起始发生在第一个内部AUG密码子处，并产生一种在氨基末端缺少42个残基的突变蛋白。这种蛋白以正常亲和力结合诱导剂异丙基-β -D -硫代半乳糖苷，并且能够维持四聚体结构；然而，它在体内不能发挥阻遏作用。这些数据表明，野生型乳糖阻遏物的氨基末端部分对于直接结合乳糖操纵基因或对于结合DNA的正确构象是必需的。
