Fowler W E, Buhle E L, Aebi U
Proc Natl Acad Sci U S A. 1984 Mar;81(6):1669-73. doi: 10.1073/pnas.81.6.1669.
We describe the preparation and structural analysis of ordered tubular arrays of the actin-DNase I complex. These structures consist of helically stacked rings; each ring is 73 A thick, has a 240 A outer and a 120 A inner diameter, and has 7-fold rotational symmetry. The actin-DNase I complex forms tubes under conditions in which actin alone aggregates into crystalline sheets-i.e., in the presence of the trivalent cation gadolinium. Moreover, upon addition of an equimolar amount of DNase I, crystalline actin sheets are slowly converted to tubes. The rings making the tubes contain a radial dyad axis that may be identical to the dyad axis of the unit cell of the crystalline actin sheet. Evidence is presented for this identification, which in turn allows tentative assignment of actin- and DNase I-containing regions in three-dimensional reconstructions of the rings. The structural analysis presented here may be useful in aligning available three-dimensional molecular models of actin determined from crystals of the actin-DNase I complex and from crystalline actin sheets with each other and ultimately within the biologically important actin filament.
我们描述了肌动蛋白-DNase I复合物有序管状阵列的制备及结构分析。这些结构由螺旋堆叠的环组成；每个环厚73埃，外径240埃，内径120埃，具有七重旋转对称性。在肌动蛋白单独聚集成晶体片层的条件下，即存在三价阳离子钆的情况下，肌动蛋白-DNase I复合物形成管状结构。此外，加入等摩尔量的DNase I后，晶体状的肌动蛋白片层会缓慢转变为管状结构。构成管子的环含有一个径向二重轴，该轴可能与晶体状肌动蛋白片层晶胞的二重轴相同。本文提供了支持这一认定的证据，这反过来又使得在环的三维重建中能够初步确定含有肌动蛋白和DNase I的区域。此处呈现的结构分析可能有助于将从肌动蛋白-DNase I复合物晶体和晶体状肌动蛋白片层确定的现有肌动蛋白三维分子模型相互对齐，并最终在生物学上重要的肌动蛋白丝内对齐。
