Flexible phenylalanine-glycine nucleoporins as entropic barriers to nucleocytoplasmic transport
Flexible phenylalanine-glycine nucleoporins as entropic barriers to nucleocytoplasmic transport
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DOI：
10.1073/pnas.0603521103
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发表时间：
2006-06-20
影响因子：
11.1
通讯作者：
Aebi, Ueli
中科院分区：
文献类型：
--
作者：
Lim, Roderick Y. H.;Huang, Ning-Ping;Aebi, Ueli
据称，天然展开的苯丙氨酸-甘氨酸（FG）重复结构域在核细胞质运输过程中形成核孔复合物中选择性屏障门的物理成分。目前，由于缺乏有关 FG 域纳米力学特性的信息，选择性门背后的生物物理机制仍然是推测性的。在这项工作中，我们应用原子力显微镜来测量单个和 FG 分子簇的机械响应。单分子力谱表明 FG 分子是展开的且高度柔韧。为了深入了解选择性门控机制，我们构建了一个实验平台来研究纳米尺度表面束缚 FG 分子的集体行为。测量表明，此类 FG 分子的集体行为会产生指数衰减的长程空间排斥力。这一发现表明分子在延伸的聚合物刷状构象中具有热流动性。通过观察刷状构象在极性较小的溶剂条件下经历可逆塌陷转变，证实了这一论断。这些发现揭示了 FG 重复结构域如何同时充当核孔复合物近场相互作用区中的熵屏障和选择性陷阱；即选择性门。
Natively unfolded phenylalanine-glycine (FG)-repeat domains are alleged to form the physical constituents of the selective barrier-gate in nuclear pore complexes during nucleocytoplasmic transport. Presently, the biophysical mechanism behind the selective gate remains speculative because of a lack of information regarding the nanomechanical properties of the FG domains. In this work, we have applied the atomic force microscope to measure the mechanical response of individual and clusters of FG molecules. Single-molecule force spectroscopy reveals that FG molecules are unfolded and highly flexible. To provide insight into the selective gating mechanism, an experimental platform has been constructed to study the collective behavior of surface-tethered FG molecules at the nanoscale. Measurements indicate that the collective behavior of such FG molecules gives rise to an exponentially decaying long-range steric repulsive force. This finding indicates that the molecules are thermally mobile in an extended polymer brush-like conformation. This assertion is confirmed by observing that the brush-like conformation undergoes a reversible collapse transition in less polar solvent conditions. These findings reveal how FG-repeat domains may simultaneously function as an entropic barrier and a selective trap in the near-field interaction zone of nuclear pore complexes; i.e., selective gate.