Sequence determinants of a conformational switch in a protein structure
Sequence determinants of a conformational switch in a protein structure
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DOI：
10.1073/pnas.0509349102
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发表时间：
2005-12-20
影响因子：
11.1
通讯作者：
Sauer, RT
中科院分区：
文献类型：
--
作者：
Anderson, TA;Cordes, MHJ;Sauer, RT
噬菌体P22的Arc抑制因子是带状-螺旋-螺旋转录因子家族的二聚体成员。每个野生型Arc亚基对的残基9-14形成两条反平行的β链，并且具有极性和非极性残基的交替模式，这对于具有一个溶剂暴露面和一个形成部分疏水核心的β带来说是预期的。同时将Asn-11转换为Leu，将Leu-12转换为Asn，将局部二值序列模式改变为两向螺旋结构。先前的研究表明，这种双重突变导致野生型β -带被两个右手3(10)-螺旋取代。此外，仅携带Asn-11右箭头Leu突变的Arc变体具有模糊的二元模式，可以形成带状结构或螺旋结构，它们可以快速交换。在这里，我们研究了Arc突变体，其中11号位置被Gly， Ala, Val, lie, Leu, Met， Phe或Tyr占据。这些突变体在稳定该褶皱的序列背景下采用野生型β -带状结构，但在阴性设计排除野生型褶皱的序列背景下，它们采用替代的螺旋结构。在其他野生型序列背景下，11位侧链的详细化学性质决定了两个相互竞争的构象折叠中哪一个是首选的。
The Arc repressor of bacteriophage P22 is a dimeric member of the ribbon-helix-helix family of transcription factors. Residues 9-14 of each wild-type Arc subunit pair to form two antiparallel beta-strands and have the alternating pattern of polar and nonpolar residues expected for a beta-ribbon with one solvent-exposed face and one face that forms part of the hydrophobic core. Simultaneously switching Asn-11 to Leu and Leu-12 to Asn changes the local binary sequence pattern to that of an amphipathic helix. Previous studies have shown that this double mutation results in replacement of the wild-type beta-ribbon by two right-handed 3(10)-helices. Moreover, an Arc variant bearing just the Asn-11 right arrow Leu mutation has an ambiguous binary pattern and can form either the ribbon or the helical structures, which interchange rapidly. Here, we study Arc mutants in which position 11 is occupied by Gly, Ala, Val, lie, Leu, Met, Phe, or Tyr. These mutants adopt the wild-type beta-ribbon structure in a sequence context that stabilizes this fold, but they assume the alternative helical structure in a sequence background in which the wild-type fold is precluded by negative design. In an otherwise wild-type sequence background, the detailed chemical properties of the position 11 side chain dictate which of the two competing conformational folds is preferred.