Hicks M R, Holberton D V, Kowalczyk C, Woolfson D N
Centre for Biomolecular Design and Drug Development, School of Biological Sciences, University of Sussex, Falmer, UK.
Fold Des. 1997;2(3):149-58. doi: 10.1016/S1359-0278(97)00021-7.
The seven-residue heptad repeat is the accepted hallmark of coiled coils. In extended filamentous proteins, however, contiguous patterns of heptads are often disrupted by 'skips' and 'stammers'. The structural consequences and roles of these digressions are not understood.
In a cytoskeleton protein from Giardia lamblia, heptads flank eleven-residue units (hendecads) to give a 7-11-7 motif that dominates the sequence. Synthetic peptides made to the consensus sequence of this motif fold in solution to fully helical, parallel dimers. Both the sequence pattern and these experimental data are consistent with the coiled-coil model. We note that breaks in other extended coiled coils can also be reconciled by hendecad insertions.
The heptad paradigm for the coiled coil must be expanded to include hendecads. As different combinations of heptads and hendecads will give different overall sequence motifs, we propose that these provide a mechanism to promote cognate protein pairings during the folding of extended coiled coils in the cell.
七残基七肽重复序列是公认的卷曲螺旋的标志。然而，在延伸的丝状蛋白质中，七肽的连续模式常常被“跳跃”和“口吃”所破坏。这些偏离的结构后果和作用尚不清楚。
在贾第虫的一种细胞骨架蛋白中，七肽位于十一残基单元（十一肽）两侧，形成7-11-7基序，该基序在序列中占主导地位。根据该基序的共有序列合成的肽在溶液中折叠成完全螺旋的平行二聚体。序列模式和这些实验数据均与卷曲螺旋模型一致。我们注意到，其他延伸的卷曲螺旋中的断裂也可以通过十一肽插入来解释。
卷曲螺旋的七肽范式必须扩展以包括十一肽。由于七肽和十一肽的不同组合将产生不同的整体序列基序，我们提出这些基序提供了一种机制，以促进细胞中延伸的卷曲螺旋折叠过程中的同源蛋白配对。
