Actins are among the most abundant and conserved proteins in eukaryotic cells, where they form filamentous structures that perform vital roles in key cellular processes. Although large amounts of data on the biochemical activities, dynamic behaviors, and important cellular functions of plant actin filaments have accumulated, their structural basis remains elusive. Here, we report a 3.9 Å structure of the plant actin filament from Zea mays pollen (ZMPA) using cryo-electron microscopy. The structure shows a right-handed, double-stranded (two parallel strands) and staggered architecture that is stabilized by intra- and interstrand interactions. While the overall structure resembles that of other actin filaments, its DNase I binding loop bends farther outward, adopting an open conformation similar to that of the jasplakinolide- or beryllium fluoride (BeFx)-stabilized rabbit skeletal muscle actin (RSMA) filament. Single-molecule magnetic tweezers analysis revealed that the ZMPA filament can resist a greater stretching force than the RSMA filament. Overall, these data provide evidence that plant actin filaments have greater stability than animal actin filaments, which might be important to their role as tracks for long-distance vesicle and organelle transportation.plantcell;31/12/2855/FX1F1fx1.

中文翻译：

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玉米花粉肌动蛋白丝的冷冻电镜结构。

肌动蛋白是真核细胞中最丰富、最保守的蛋白质之一，它们形成丝状结构，在关键细胞过程中发挥重要作用。尽管已经积累了大量关于植物肌动蛋白丝的生化活性、动态行为和重要细胞功能的数据，但它们的结构基础仍然难以捉摸。在这里，我们使用冷冻电子显微镜报告了来自玉米花粉 (ZMPA) 的植物肌动蛋白丝的 3.9 Å 结构。该结构显示出右旋、双链（两条平行链）和交错结构，通过链内和链间相互作用而稳定。虽然整体结构类似于其他肌动蛋白丝，但其 DNase I 结合环向外弯曲得更远，采用类似于 jasplakinolide 或氟化铍 (BeFx) 稳定的兔骨骼肌肌动蛋白 (RSMA) 丝的开放构象。单分子磁镊分析表明，ZMPA 细丝比 RSMA 细丝可以抵抗更大的拉伸力。总体而言，这些数据提供的证据表明植物肌动蛋白丝比动物肌动蛋白丝具有更高的稳定性，这对于它们作为长距离囊泡和细胞器运输轨迹的作用可能很重要。plantcell;31/12/2855/FX1F1fx1。