CRYOELECTRONMICROSCOPY OF ACTOS1 ATPASE INTERMEDIATES

描述(摘自摘要)：肌肉力量的分子基础是 肌球蛋白头附着肌动蛋白时的构型变化。这样的一个 变化可以是头部本身的构象变化，也可以是 可能是肌动蛋白结合角度的改变。力的能量 已知的生产来自于三磷酸腺苷的水解性，但同时“倾斜 “跨桥”假说仍然很有吸引力，但仍未得到证实。此外， 最近的结构数据表明，附着的肌球蛋白的构型 在ATP和ADP-PI状态下，头部可能是相似的。 检验倾斜桥假说的一个问题是 建立所谓的弱结合肌球蛋白状态的结构 在三磷酸腺苷存在的情况下发生。有相当多的人知道关于 出现在ADP或无核苷酸中的强结合态的结构。 然而，其他束缚态也是难以捉摸的，因为它们在 中分辨率显微镜所需的低蛋白质浓度 Acto-Myosin Head(S1)复合体或它们仅短暂存在。这个 申请者最近发现了一些条件，可以让人观察到短暂的和 弱束缚态并一直在用电子研究它们的结构 水化标本的冷冻显微镜。已经获得的显微照片显示 在稳态ATP水解过程中附着的S1构型的变化；例如 因此，数据符合倾斜桥假说，但不符合 证明给我看。

DESCRIPTION (Adapted from abstract): The molecular basis of muscle force is a configurational change in the myosin head while attached to actin. Such a change could either be a conformational change within the head itself, or it may be an alteration in the binding angle made with actin. The energy for force production is known to come from ATP hydrolysis, but while the "tilting cross-bridge" hypothesis remains attractive, it is still unproven. Moreover, recent structural data have suggested that the configuration of attached myosin heads may be similar in both the ATP and ADP-Pi states. One problem in testing the tilting bridge hypothesis has been the difficulty of establishing the structures of so-called weakly bound acto-myosin states that occur in the presence of ATP. A considerable amount is known about the structure of the strongly bound states that occur in ADP or no nucleotide. However, other bound states have been elusive either because they dissociate at the low protein concentrations required for moderate resolution microscopy of the acto-myosin head (S1) complex or they are present only transiently. The applicant recently found conditions that allow one to observe transient and weakly bound states and has been studying their structures by electron cryo-microscopy of hydrated specimens. The micrographs already obtained show a variety of attached S1 configurations during steady-state ATP hydrolysis; such data are therefore compatible with the tilting bridge hypothesis but do not prove it.