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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >A seven-helix coiled coil
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A seven-helix coiled coil

机译：七螺旋线圈

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摘要

Coiled-coil proteins contain a characteristic seven-residue sequence repeat whose positions are designated a to g. The interacting surface between alpha-helices in a classical coiled coil is formed by interspersing nonpolar side chains at the a and d positions with hydrophilic residues at the flanking e and g positions. To explore how the chemical nature of these core amino acids dictates the overall coiled-coil architecture, we replaced all eight e and g residues in the GCN4 leucine zipper with nonpolar alanine side chains. Surprisingly, the alanine-containing mutant forms a stable alpha-helical heptamer in aqueous solution. The 1.25-angstrom resolution crystal structure of the heptamer reveals a parallel seven-stranded coiled coil enclosing a large tubular channel with an unusual heptad register shift between adjacent staggered helices. The overall geometry comprises two interleaved hydrophobic helical screws of interacting cross-sectional a and d layers that have not been seen before. Moreover, asparagines at the a positions play an essential role in heptamer formation by participating in a set of buried interhelix hydrogen bonds. These results demonstrate that heptad repeats containing four hydrophobic positions can direct assembly of complex, higher-order coiled-coil structures with rich diversity for close packing of alpha-helices.
机译：卷曲螺旋蛋白包含一个特征性的七残基序列重复序列，其位置标记为a至g。在经典螺旋线圈中，α螺旋之间的相互作用表面是通过在a和d位置散布非极性侧链以及在e和g位置旁的亲水性残基形成的。为了探索这些核心氨基酸的化学性质如何决定整个螺旋线圈结构，我们用非极性丙氨酸侧链替换了GCN4亮氨酸拉链中的所有8个e和g残基。令人惊讶地，含丙氨酸的突变体在水溶液中形成稳定的α-螺旋七聚体。七聚体的1.25埃分辨率晶体结构揭示了一个平行的七股螺旋形线圈，它包围着一个大的管状通道，在相邻的交错螺旋之间存在不寻常的七聚体移位。总体几何形状包括两个交错的疏水性螺旋螺钉，它们相互之间的横截面a和d层从未见过。而且，在a位的天冬酰胺通过参与一组埋入的螺旋间氢键在七聚体的形成中起重要作用。这些结果表明，含有四个疏水位点的七肽重复序列可以指导复杂的，高阶卷曲螺旋结构的组装，这些结构具有丰富的多样性，可以紧密堆积α-螺旋。

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