Orientational disorder and motion of weakly attached cross-bridges.
Orientational disorder and motion of weakly attached cross-bridges.
复制标题
弱附着横桥的定向障碍和运动。
DOI：
10.1016/s0006-3495(91)82093-8
复制
发表时间：
1991
影响因子：
3.4
通讯作者：
Thomas,DD
中科院分区：
文献类型：
--
作者：
Fajer,PG;Fajer,EA;Schoenberg,M;Thomas,DD
在低离子强度的松弛肌肉纤维中，交叉桥很可能处于与交叉桥动力中风之前的状态相当的状态(勋伯格，M.1988)。高级经验地中海医院。比奥尔。226：189-202)。用电子顺磁共振(EPR)和(饱和转移)电子顺磁共振(ST-EPR)技术对马来酰亚胺自旋标记纤维，在低离子强度条件下，我们已经确定：(A)松弛标记的纤维表现出与未标记的松弛纤维相同的弦部硬度的速度依赖关系，这意味着类似的交叉桥的快速解离和重新解离；(B)在低离子强度下附着的松弛头部几乎与在生理离子强度下的松弛一样无序，其中大多数头部与肌动蛋白分离；(C)与正常离子强度相比，放松的头部的微秒旋转流动性仅受到轻微限制，这意味着尽管附着，但仍有很大的运动自由。低离子强度和正常离子强度的头部迁移率的差异与细丝重叠，因此是由于肌球蛋白相互作用造成的。光谱可以用两个群体来模拟：一个与正常离子强度下的松弛头部相同(83%)，另一个代表更定向的头部群体(17%)。后者的光谱与严格意义上的光谱以大致相同的角度为中心，但相对于光纤轴表现出更大的(40度)轴向探测无序。
In a relaxed muscle fiber at low ionic strength, the cross-bridges may well be in states comparable to the one that precedes the cross-bridge power stroke (Schoenberg, M. 1988. Adv. Exp. Med. Biol. 226:189–202). Using electron paramagnetic resonance (EPR) and (saturation transfer) electron paramagnetic resonance (ST-EPR) techniques on fibers labeled with maleimide spin label, under low ionic strength conditions designed to produce a majority of weakly-attached heads, we have established that (a) relaxed labeled fibers show a speed dependence of chord stiffness identical to that of unlabeled, relaxed fibers, suggesting similar rapid dissociation and reassociation of cross-bridges; (b) the attached relaxed heads at low ionic strength are nearly as disordered as in relaxation at physiological ionic strength where most of the heads are detached from actin; and (c) the microsecond rotational mobility of the relaxed heads was only slightly restricted compared to normal ionic strength, implying great motional freedom despite attachment. The differences in head mobility between low and normal ionic strength scale with filament overlap and are thus due to acto-myosin interactions. The spectra can be modeled in terms of two populations: one identical to relaxed heads at normal ionic strength (83%), the other representing a more oriented population of heads (17%). The spectrum of the latter is centered at approximately the same angle as the spectrum in rigor but exhibits larger (40 degrees) axial probe disorder with respect to the fiber axis.(ABSTRACT TRUNCATED AT 250 WORDS)