Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02454-9110, USA.
Protein Sci. 2010 Jul;19(7):1366-75. doi: 10.1002/pro.415.
A quantitative analysis of the direction of bending of two-stranded alpha-helical coiled coils in crystal structures has been carried out to help determine how the amino acid sequence of the coiled coil influences its shape and function. Change in the axial staggering of the coiled coil, occurring at the boundaries of either clusters of core alanines in tropomyosin or of clusters of core bulky residues in the myosin rod, causes bending within the plane of the local dimer. The results also reveal that large gaps in the core of the coiled coil, which are seen for small core residues near large core residues or for unbranched core residues near canonical branched core residues, are correlated with bending out of the local dimeric plane. Comparison of tropomyosin structures determined in independent crystal environments provides further evidence for the concept that sequence directs the bending of the coiled coil, but that crystal environment is at least as important as sequence for determining the magnitude of bending. Tropomyosin thus appears to consist of more directionally restrained hinge-like joints rather than directionally variable universal joints, which helps account for and predicts the geometric and dynamic nature of its binding to F-actin.
对晶体结构中双股α-螺旋卷曲螺旋的弯曲方向进行了定量分析，以帮助确定卷曲螺旋的氨基酸序列如何影响其形状和功能。在原肌球蛋白中核心丙氨酸簇或肌球蛋白杆中核心大体积残基簇的边界处发生的卷曲螺旋的轴向错开变化导致局部二聚体平面内的弯曲。结果还表明，在核心小残基靠近大核心残基或无支链核心残基靠近规范支链核心残基的情况下，核心中出现的较大间隙与局部二聚体平面外的弯曲有关。在独立晶体环境中确定的原肌球蛋白结构的比较为这样一种概念提供了进一步的证据，即序列指导卷曲螺旋的弯曲，但晶体环境对于确定弯曲程度至少与序列一样重要。因此，原肌球蛋白似乎由更多方向受限制的铰链状接头组成，而不是方向可变的通用接头，这有助于解释和预测其与 F-肌动蛋白结合的几何和动态性质。
