Nelson H C, Hecht M H, Sauer R T
Cold Spring Harb Symp Quant Biol. 1983;47 Pt 1:441-9. doi: 10.1101/sqb.1983.047.01.052.
We have characterized about 50 different amino acid substitutions in the aminoterminal domain of lambda repressor. Sixteen of these substitutions alter external side chains of the repressor and cause a substantial reduction in the affinity of the mutant repressor for operator DNA. Seven of these mutant repressors were purified and were shown to be stably folded. The strong, external repressor mutations occur near the aminoterminal end of alpha helix 2, throughout alpha helix 3, and in the aminoterminal-arm region of the repressor. These results suggest that these regions of lambda repressor are close to operator DNA in the protein-DNA complex and thus that these regions comprise the DNA-binding sites of the repressor. Our genetic results support and are completely consistent with more-detailed models of the repressor-operator interaction based on model-building (Pabo and Lewis 1982; Lewis et al. this volume) and biochemical studies (Pabo et al. 1982).
我们已对λ阻遏物氨基末端结构域中约50种不同的氨基酸取代进行了表征。其中16种取代改变了阻遏物的外侧链，并导致突变型阻遏物与操纵基因DNA的亲和力大幅降低。纯化了其中7种突变型阻遏物，并证明它们能稳定折叠。强烈的外侧阻遏物突变发生在α螺旋2的氨基末端附近、整个α螺旋3以及阻遏物的氨基末端臂区域。这些结果表明，在蛋白质-DNA复合物中，λ阻遏物的这些区域靠近操纵基因DNA，因此这些区域构成了阻遏物的DNA结合位点。我们的遗传学结果支持基于模型构建（帕博和刘易斯，1982年；刘易斯等人，本卷）和生化研究（帕博等人，1982年）得出的关于阻遏物-操纵基因相互作用的更详细模型，并且与之完全一致。
