Three-stranded coiled coils are peptide structures constructed from amphipathic heptad repeats. Here we show that it is possible to form pure heterotrimeric three-stranded coiled coils by combining three distinct characteristics: (1) a cysteine sulfur layer for metal coordination, (2) a thiophilic, trigonal pyramidal metalloid (Pb(II)) that binds to these sulfurs and (3) an adjacent layer of reduced steric bulk generating a cavity where water can hydrogen bond to the cysteine sulfur atoms. Cysteine substitution in an a site yields Pb(II)A2B heterotrimers, while d sites provide pure Pb(II)C2D or Pb(II)CD2 scaffolds. Altering the metal from Pb(II) to Hg(II) or shifting the relative position of the sterically less demanding layer removes heterotrimer specificity. Because only two of the eight or ten hydrophobic layers are perturbed, catalytic sites can be introduced at other regions of the scaffold. A Zn(II)(histidine)3(H2O) centre can be incorporated at a remote location without perturbing the heterotrimer selectivity, suggesting a unique strategy to prepare dissymmetric catalytic sites within self-assembling de novo-designed proteins.

中文翻译：

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使用Pb（II）（Cys）3模板介导的策略设计的异型三链卷曲螺旋。

三链卷曲螺旋是由两亲性七肽重复序列构建的肽结构。在这里，我们表明可以通过组合三个不同的特征来形成纯的异三聚体三链卷曲线圈：（1）用于金属配位的半胱氨酸硫层；（2）结合的亲硫的三角锥类金属（Pb（II）） （3）减少空间体积的相邻层，形成一个空腔，在空腔中水可以氢键合到半胱氨酸硫原子上。一个位点的半胱氨酸取代产生Pb（II）A2B异源三聚体，而d个位点提供纯的Pb（II）C2D或Pb（II）CD2支架。将金属从Pb（II）变为Hg（II）或改变对空间要求较低的层的相对位置可消除异源三聚体特异性。由于八个或十个疏水层中只有两个受到干扰，催化位点可引入支架的其他区域。Zn（II）（组氨酸）3（H2O）中心可在不影响异源三聚体选择性的情况下并入偏远地区，这表明在自组装从头设计的蛋白质中制备不对称催化位点的独特策略。