Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
Department of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT, 06520-8103, USA.
Nat Commun. 2024 Mar 6;15(1):2059. doi: 10.1038/s41467-024-46179-x.
Arp2/3 complex nucleates branched actin filaments for cell and organelle movements. Here we report a 2.7 Å resolution cryo-EM structure of the mature branch junction formed by S. pombe Arp2/3 complex that provides details about interactions with both mother and daughter filaments. We determine a second structure at 3.2 Å resolution with the phosphate analog BeF bound with ADP to Arp3 and ATP bound to Arp2. In this ADP-BeF transition state the outer domain of Arp3 is rotated 2° toward the mother filament compared with the ADP state and makes slightly broader contacts with actin in both the mother and daughter filaments. Thus, dissociation of P from the ADP-P transition state reduces the interactions of Arp2/3 complex with the actin filaments and may contribute to the lower mechanical stability of mature branch junctions with ADP bound to the Arps. Our structures also reveal that the mother filament in contact with Arp2/3 complex is slightly bent and twisted, consistent with the preference of Arp2/3 complex binding curved actin filaments. The small degree of twisting constrains models of actin filament mechanics.
Arp2/3 复合物为细胞和细胞器的运动引发分支肌动蛋白丝。在这里，我们报道了一个成熟分支连接点的 2.7Å 分辨率冷冻电镜结构，由 S. pombe Arp2/3 复合物形成，提供了关于与母丝和子丝相互作用的详细信息。我们确定了第二个结构，分辨率为 3.2Å，并用结合 ADP 的磷酸盐类似物 BeF 结合到 Arp3 上，以及结合到 Arp2 的 ATP。在这个 ADP-BeF 过渡态中，与 ADP 状态相比，Arp3 的外域向母丝旋转了 2°，并与母丝和子丝中的肌动蛋白产生略微更广泛的接触。因此，从 ADP-P 过渡态中释放 P 降低了 Arp2/3 复合物与肌动蛋白丝的相互作用，并且可能导致与 ADP 结合的 Arp 结合的成熟分支连接点的机械稳定性降低。我们的结构还表明，与 Arp2/3 复合物接触的母丝稍微弯曲和扭曲，与 Arp2/3 复合物结合弯曲肌动蛋白丝的偏好一致。小程度的扭曲限制了肌动蛋白丝力学模型。
Zotero 插件
