Heimburg T, Schünemann J, Weber K, Geisler N
Max Planck Institute for Biophysical Chemistry Departments of Spectroscopy and Biochemistry D-37018 Goettingen, Federal Republic of Germany.
Biochemistry. 1999 Sep 28;38(39):12727-34. doi: 10.1021/bi983079h.
Coiled coils of different order were investigated using infrared (IR) spectroscopy. Recently, we demonstrated that dimeric coiled coils display unique vibrational spectra with at least three separable bands instead of only one band of a classical alpha-helix in the amide I region. This was attributed to a distortion of the helical structure by the supercoil bending, giving rise to bands that are not observed in the undistorted helix. Here, we investigated coiled coils forming trimers, tetramers, and pentamers. These higher order coiled coils, in general, possess larger superhelical pitches, resulting in a smaller helical distortion. We found that all coiled coils studied, including the native dimeric GCN4 leucine zipper and its variants leading to parallel trimers and tetramers as well as the rod portions of fibritin (parallel trimer), alpha-actinin (antiparallel spectrin type trimer), and COMP (parallel pentamer), displayed the typical three band pattern of the coiled coil amide I spectra. However, the separation of these three bands and their positional deviation from the classical alpha-helical band position was correlated to the extent of the helical distortion as reflected by the pitch values of the supercoils. The most pronounced spectral anomaly was found for the tropomyosin dimer with a reported helical pitch of 137 A, whereas the smallest spectral distortion was found for the pentameric COMP complex and the tetrameric leucine zipper mutant, both with a pitch of about 205 A.
利用红外（IR）光谱对不同层级的卷曲螺旋进行了研究。最近，我们证明二聚体卷曲螺旋在酰胺I区域显示出独特的振动光谱，具有至少三个可分离的谱带，而不是经典α-螺旋的仅一个谱带。这归因于超螺旋弯曲导致的螺旋结构扭曲，产生了在未扭曲螺旋中未观察到的谱带。在此，我们研究了形成三聚体、四聚体和五聚体的卷曲螺旋。一般来说，这些高阶卷曲螺旋具有更大的超螺旋螺距，导致较小的螺旋扭曲。我们发现，所有研究的卷曲螺旋，包括天然二聚体GCN4亮氨酸拉链及其导致平行三聚体和四聚体的变体，以及血纤蛋白（平行三聚体）、α-辅肌动蛋白（反平行血影蛋白型三聚体）和软骨寡聚基质蛋白（COMP，平行五聚体）的杆状部分，都显示出卷曲螺旋酰胺I光谱典型的三个谱带模式。然而，这三个谱带的分离及其与经典α-螺旋谱带位置的位置偏差与超螺旋螺距值所反映的螺旋扭曲程度相关。对于肌动蛋白二聚体，报道的螺旋螺距为137 Å，发现了最明显的光谱异常，而对于五聚体COMP复合物和四聚体亮氨酸拉链突变体，两者螺距约为205 Å，发现了最小的光谱扭曲。
