Orientational information of troponin C within the thin filaments obtained by neutron fiber diffraction.
Orientational information of troponin C within the thin filaments obtained by neutron fiber diffraction.
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通过中子纤维衍射获得细丝内肌钙蛋白 C 的方向信息。
DOI：
10.1016/j.jmb.2006.12.072
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发表时间：
2007
影响因子：
5.6
通讯作者：
F. Matsumoto
中科院分区：
文献类型：
--
作者：
S. Fujiwara;F. Matsumoto
在横纹肌中，收缩由薄的基于胶原的蛋白质、由三个亚基（TnC、TnI和TnT）组成的肌钙蛋白和原肌球蛋白调节。这些蛋白质的原位结构的知识是必不可少的，阐明这种Ca 2+敏感的调节机制。我们采用中子散射研究的结构TnC内的细丝，并发现TnC假设延长哑铃状结构和移动的细丝轴通过绑定的Ca 2+。在这里，为了获得更详细的原位结构信息的TnC，中子纤维衍射测量进行。在2 H2O中制备了天然细丝和含氘代TnC的细丝溶胶。通过将这些溶胶密封在直径为3 mm的石英毛细管中，在18特斯拉的磁场中，获得取向的样品。中子纤维衍射图案，从这些取向的样品中获得的存在和不存在的Ca 2+。所获得的图案表现出强烈的赤道衍射由于细丝，59个和51个的层线由于肌动蛋白，和赤道反射由于Tn-复合物。通过模型计算分析了TnC复合物的双折射，结果表明，在无Ca ~（2+）和有Ca ~（2+）存在时，TnC的长轴与细丝轴之间的夹角分别为67（±7）°和49（±17）°，表明TnC在无Ca ~（2+）存在时的取向与细丝轴垂直，通过结合Ca ~（2+），纤维向纤维轴倾斜，取向和位置无序增加。与Ca ~（2+）结合后，TnC的相对位置移动了约22 μ m，这种明显的移动是伴随着其它TnC亚基的移动而发生的。这意味着通过结合Ca 2+，Tn-亚基发生显著的结构重排。
In striated muscles contraction is regulated by the thin filament-based proteins, troponin consisting of three subunits (TnC, TnI, and TnT), and tropomyosin. Knowledge of in situ structures of these proteins is indispensable for elucidating this Ca2+-sensitive regulatory mechanism. We employed neutron scattering to investigate the structure of TnC within the thin filament, and found that TnC assumes extended dumbbell-like structures and moves toward the filament axis by binding of Ca2+. Here, in order to obtain more detailed in situ structural information of TnC, neutron fiber diffraction measurements were performed. Sols of native thin filaments and the thin filaments containing deuterated TnC were prepared in2H2O. The oriented samples were obtained by placing these sols sealed in quartz capillaries with a diameter of 3 mm in a magnetic field of 18 Tesla. Neutron fiber diffraction patterns were obtained from these oriented samples in the absence and presence of Ca2+. The patterns obtained showed strong equatorial diffraction due to the thin filaments, 59 Å and 51 Å layer-lines due to actin, and meridional reflections due to Tn-complex. Analysis of the meridional reflections due to Tn-complex with aid of model calculation showed that the angle between the thin filament axis and the long axis of TnC was estimated to be 67(±7)° and 49(±17)°, in the absence and presence of Ca2+, respectively, suggesting that TnC, which assumes orientations rather perpendicular to the filament axis in the absence of Ca2+, tilts toward the filament axis and the orientational and positional disorder increases by binding Ca2+. It also showed that the relative position of the TnC moved by about 22 Å by binding Ca2+, and this apparent movement was concomitant with the movements of other Tn-subunits. This implies that by binding Ca2+, significant structural rearrangements of Tn-subunits occur.
影响因子：
2.9
作者：
Spyracopoulos, L;Li, MX;Sykes, BD
通讯作者：
Sykes, BD