A seven-helix coiled coil
A seven-helix coiled coil
复制标题
DOI：
10.1073/pnas.0604871103
复制
发表时间：
2006-10-17
影响因子：
11.1
通讯作者：
Lu, Min
中科院分区：
文献类型：
--
作者：
Liu, Jie;Zheng, Qi;Lu, Min
卷曲螺旋蛋白含有一个特征性的七个残基的序列重复，其位置被指定为a至g。经典卷曲螺旋中α-螺旋之间的相互作用表面是通过在a和d位置处散布非极性侧链与在侧翼e和g位置处的亲水残基形成的。为了探索这些核心氨基酸的化学性质如何决定整体卷曲螺旋结构，我们用非极性丙氨酸侧链替换了GCN 4亮氨酸拉链中的所有8个e和g残基。令人惊讶的是，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埃分辨率的晶体结构揭示了一个平行的七股卷曲螺旋，它包围着一个大的管状通道，在相邻的交错螺旋之间有一个不寻常的七肽寄存器移位。整体几何结构包括两个交错的疏水螺旋螺杆的相互作用的横截面a和d层，以前没有见过。此外，天冬酰胺在a位置通过参与一组埋藏的螺旋间氢键在七聚体形成中起重要作用。这些结果表明，含有四个疏水位置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，其具有丰富的多样性，用于α-螺旋的紧密堆积。
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.