Ogihara N L, Weiss M S, Degrado W F, Eisenberg D
UCLA-DOE Laboratory of Structural Biology and Molecular Medicine 90095-1570, USA.
Protein Sci. 1997 Jan;6(1):80-8. doi: 10.1002/pro.5560060109.
The three-dimensional structure of the 29-residue designed coiled coil having the amino acid sequence acetyl-E VEALEKK VAALESK VQALEKK VEALEHG-amide has been determined and refined to a crystallographic R-factor of 21.4% for all data from 10-A to 2.1-A resolution. This molecule is called coil-VaLd because it contains valine in the a heptad positions and leucine in the d heptad positions. In the trigonal crystal, three molecules, related by a crystallographic threefold axis, form a parallel three-helix bundle. The bundles are stacked head-to-tail to form a continuous coiled coil along the c-direction of the crystal. The contacts among the three helices within the coiled coil are mainly hydrophobic: four layers of valine residues alternate with four layers of leucine residues to form the core of the bundle. In contrast, mostly hydrophilic contacts mediate the interaction between trimers: here a total of two direct protein--protein hydrogen bonds are found. Based on the structure, we propose a scheme for designing crystals of peptides containing continuous two-, three-, and four-stranded coiled coils.
已确定并精制了具有乙酰基 - E VEALEKK VAALESK VQALEKK VEALEHG - 酰胺氨基酸序列的29个残基设计卷曲螺旋的三维结构，对于从10 Å到2.1 Å分辨率的所有数据，其晶体学R因子为21.4%。该分子被称为coil - VaLd，因为它在a七肽位置含有缬氨酸，在d七肽位置含有亮氨酸。在三方晶体中，由晶体学三重轴相关的三个分子形成一个平行的三螺旋束。这些束头对头堆叠，沿晶体的c方向形成连续的卷曲螺旋。卷曲螺旋内三个螺旋之间的接触主要是疏水的：四层缬氨酸残基与四层亮氨酸残基交替形成束的核心。相比之下，三聚体之间的相互作用主要由亲水接触介导：这里总共发现了两个直接的蛋白质 - 蛋白质氢键。基于该结构，我们提出了一种设计包含连续两链、三链和四链卷曲螺旋的肽晶体的方案。
