Dimerisation mutants of Lac repressor. II. A single amino acid substitution, D278L, changes the specificity of dimerisation
Dimerisation mutants of Lac repressor. II. A single amino acid substitution, D278L, changes the specificity of dimerisation
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DOI：
10.1006/jmbi.1999.3469
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发表时间：
2000-02-18
影响因子：
5.6
通讯作者：
Muller-Hill, B
中科院分区：
文献类型：
--
作者：
Spott, S;Dong, FM;Muller-Hill, B
乳糖阻遏物四聚体的组装涉及两个亚基界面，C-末端七肽重复序列和单体-单体界面。缺乏两个C-末端七肽重复序列的大肠杆菌Lac阻遏物的两个单体之间的二聚化通过每个单体的三个α-螺旋之间的相互作用发生，这形成了高度疏水的界面。可能参与特异性二聚体形成的残基是从X射线研究和超过4000个单氨基酸取代的表型中已知的。在检查大量的突变体内的二聚化界面的乳糖阻遏物，我们发现，取代一个氨基酸，D278亮氨酸，足以改变特异性的二聚化。这一单一取代的分析表明，D278 L突变体Lac阻遏物像野生型一样阻遏。然而，它不再与野生型Lac阻遏物形成异二聚体。(C)北京大学出版社.
Assembly of the lactose repressor tetramer involves two subunit interfaces, the C-terminal heptad repeats, and the monomer-monomer interface. Dimerisation between two monomers of Lac repressor of Escherichia coli lacking the two C-terminal heptad repeats occurs through the interactions between three alpha-helices of each monomer, which form a highly hydrophobic interface. Residues possibly involved in specific dimer formation are known from X-ray studies and from the phenotypes of more than 4000 single amino add substitutions. During the examination of numerous mutants within the dimerisation interface of Lac repressor, we found that substitution of one amino acid, D278 to leucine, is sufficient to change the specificity of dimerisation. Analysis of this single substitution indicates that D278L mutant Lac repressor represses like wild-type. However, it no longer forms heterodimers with wild-type Lac repressor. (C) 2000 Academic Press.