Liu Jie, Yong Wei, Deng Yiqun, Kallenbach Neville R, Lu Min
Department of Biochemistry, Weill Medical College of Cornell University, New York, NY 10021, USA.
Proc Natl Acad Sci U S A. 2004 Nov 16;101(46):16156-61. doi: 10.1073/pnas.0405319101. Epub 2004 Nov 1.
Coiled-coil motifs are ubiquitous mediators of specific protein-protein interactions through the formation of interlocking hydrophobic seams between alpha-helical chains. Residues that form these seams occur at the first (a) and fourth (d) positions of a characteristic 7-aa repeat and are primarily aliphatic. The potential of aromatic residues to promote helix association in a coiled coil was explored by engineering a "Trp-zipper" protein with Trp residues at all 14 a and d positions. The protein forms a discrete, stable, alpha-helical pentamer in water at physiological pH. Its 1.45-A crystal structure reveals a parallel, five-stranded coiled coil, a previously uncharacterized type of "knobs-into-holes" packing interaction between interfacial Trp side chains, and an unusual approximately 8-A-diameter axial channel lined with indole rings that is filled with polyethylene glycol 400 and water and sulfate ion molecules. The engineered Trp-zipper pentamer enlarges current views of coiled-coil assembly, molecular recognition, and protein engineering, and may serve as a soluble model for membrane ion channels.
卷曲螺旋基序是通过在α-螺旋链之间形成互锁的疏水接缝来介导特定蛋白质-蛋白质相互作用的普遍存在的介质。形成这些接缝的残基出现在特征性7个氨基酸重复序列的第一个（a）和第四个（d）位置，主要是脂肪族的。通过构建在所有14个a和d位置都有色氨酸残基的“色氨酸拉链”蛋白，探索了芳香族残基促进卷曲螺旋中螺旋缔合的潜力。该蛋白在生理pH值的水中形成离散、稳定的α-螺旋五聚体。其1.45埃的晶体结构揭示了一个平行的五链卷曲螺旋、界面色氨酸侧链之间以前未表征的“旋钮-入-孔”堆积相互作用，以及一个由吲哚环排列的异常的直径约8埃的轴向通道，该通道填充有聚乙二醇400、水和硫酸根离子分子。工程化的色氨酸拉链五聚体扩展了目前对卷曲螺旋组装、分子识别和蛋白质工程的认识，并可能作为膜离子通道的可溶性模型。
