Direct observation of subunit exchange along mature vimentin intermediate filaments.
Direct observation of subunit exchange along mature vimentin intermediate filaments.
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DOI：
10.1016/j.bpj.2014.09.050
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发表时间：
2014-12-16
影响因子：
3.4
通讯作者：
Koester, Sarah
中科院分区：
文献类型：
--
作者：
Noeding, Bernd;Herrmann, Harald;Koester, Sarah
肌动蛋白丝、微管和中间丝是后生动物细胞骨架的核心组成部分。在分子水平上，肌动蛋白丝和微管的组装机制与IFs的组装机制根本不同。前两种类型的细丝由球状蛋白质组装而成。相比之下，IF组装从四聚体复合物的扩展，半交错，和反平行取向的卷曲螺旋。这些四聚体横向关联成单位长度的长丝，随后的纵向退火单位长度的长丝产生成熟的IF。在体外，IF形成开放的结构，没有固定数量的四聚体沿丝沿着每个横截面。因此，IF结构生物学的一个中心问题是单个亚基是否可以从组装的细丝中解离并在其他位点重新结合。使用荧光标记的IF-蛋白波形蛋白的组装，我们直接观察和定量确定丝之间的亚基交换事件，以及与可溶性波形蛋白池。因此，我们证明了供体和受体细丝的横截面多态性起着重要的作用。我们建议，在超过标准的32个分子每个横截面的捐助者细丝的片段，亚基是不是紧密结合，并倾向于被释放的细丝。
Actin filaments, microtubules, and intermediate filaments (IFs) are central elements of the metazoan cytoskeleton. At the molecular level, the assembly mechanism for actin filaments and microtubules is fundamentally different from that of IFs. The former two types of filaments assemble from globular proteins. By contrast, IFs assemble from tetrameric complexes of extended, half-staggered, and antiparallel oriented coiled-coils. These tetramers laterally associate into unit-length filaments; subsequent longitudinal annealing of unit-length filaments yields mature IFs. In vitro, IFs form open structures without a fixed number of tetramers per cross-section along the filament. Therefore, a central question for the structural biology of IFs is whether individual subunits can dissociate from assembled filaments and rebind at other sites. Using the fluorescently labeled IF-protein vimentin for assembly, we directly observe and quantitatively determine subunit exchange events between filaments as well as with soluble vimentin pools. Thereby we demonstrate that the cross-sectional polymorphism of donor and acceptor filaments plays an important role. We propose that in segments of donor filaments with more than the standard 32 molecules per cross-section, subunits are not as tightly bound and are predisposed to be released from the filament.
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