Stob S, Scheek R M, Boelens R, Kaptein R
Department of Physical Chemistry, University of Groningen, The Netherlands.
FEBS Lett. 1988 Oct 24;239(1):99-104. doi: 10.1016/0014-5793(88)80553-2.
Lac repressor headpiece (HP) and intact lac repressor have been studied using the photo-CIDNP method. At neutral pH histidine 29, tyrosines 7, 12 and 17 and methionine 1 are polarised. His-29 polarizations are weaker and broader in HP59 than in HP51 indicating that the C-terminal octapeptide in HP59 adopts a conformation that allows an interaction with His-29. The photo-CIDNP spectra of intact lac repressor and HP51 are very similar, showing that the same residues are accessible to the photo-excited flavin. An equimolar mixture of HP51 and a 14 base pair lac operator fragment strongly suppresses the photo-CIDNP effect of tyrosines 7 and 17 and abolishes the His-29 polarizations. The results are compared with earlier photo-CIDNP measurements on a complex of headpiece with poly[d(AT)] and with a model derived from a 2D NMR study on a lac headpiece-operator complex.
已使用光化学诱导动态核极化（photo-CIDNP）方法对乳糖阻遏蛋白头部结构域（HP）和完整的乳糖阻遏蛋白进行了研究。在中性pH条件下，组氨酸29、酪氨酸7、12和17以及甲硫氨酸1发生极化。与HP51相比，HP59中His-29的极化较弱且较宽，这表明HP59中的C末端八肽采取了一种允许与His-29相互作用的构象。完整的乳糖阻遏蛋白和HP51的光化学诱导动态核极化光谱非常相似，表明相同的残基可被光激发的黄素所接近。HP51与一个14碱基对的乳糖操纵基因片段的等摩尔混合物强烈抑制酪氨酸7和17的光化学诱导动态核极化效应，并消除His-29的极化。将这些结果与早期对头部结构域与聚[d(AT)]复合物的光化学诱导动态核极化测量结果以及从乳糖头部结构域-操纵基因复合物的二维核磁共振研究得出的模型进行了比较。
