Scar, a WASp-related protein, activates nucleation of actin filaments by the Arp2/3 complex
Scar, a WASp-related protein, activates nucleation of actin filaments by the Arp2/3 complex
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DOI：
10.1073/pnas.96.7.3739
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发表时间：
1999-03-30
影响因子：
11.1
通讯作者：
Pollard, TD
中科院分区：
文献类型：
--
作者：
Machesky, LM;Mullins, RD;Pollard, TD
Arp 2/3复合物是两个肌动蛋白相关蛋白（Arp 2和Arp 3）与其他五个亚基的稳定组装体，它覆盖肌动蛋白丝的尖端，并以低效率使肌动蛋白聚合成核。WASp和Scar是结合Arp 2/3复合物的p21亚基的两种类似蛋白，但它们对复合物的成核活性的影响尚不清楚。我们报告说，全长，重组人疤痕蛋白，以及N-末端截短的疤痕蛋白，增强Arp 2/3复合物的成核。这些蛋白质本身要么没有作用，要么抑制肌动蛋白聚合。Scar蛋白C端的肌动蛋白单体结合W结构域和p21结合A结构域是激活Arp 2/3复合物所必需的。Scar中间富含脯氨酸的结构域增强了W和A结构域的活性。预孵育疤痕和Arp 2/3复合物与肌动蛋白丝克服了聚合的初始滞后，这表明Arp 2/3复合物的有效成核需要在预先存在的顺式-树枝状成核机制的一侧组装。Arp 2/3复合物与全长疤痕，疤痕含有P，W和A结构域，或疤痕含有W和A结构域克服抑制成核的肌动蛋白单体结合蛋白profilin，使主动成核自发成核的低背景。这些结果表明，疤痕和，可能的，相关的蛋白质，如Cdc 42目标WASp和N-WASp，是内源性激活剂肌动蛋白聚合的Arp 2/3复合物。
The Arp2/3 complex, a stable assembly of two actin-related proteins (Arp2 and Arp3) with five other subunits, caps the pointed end of actin filaments and nucleates actin polymerization with low efficiency. WASp and Scar are two similar proteins that bind the p21 subunit of the Arp2/3 complex, but their effect on the nucleation activity of the complex was not known. We report that full-length, recombinant human Scar protein, as well as N-terminally truncated Scar proteins, enhance nucleation by the Arp2/3 complex. By themselves, these proteins either have no effect or inhibit actin polymerization. The actin monomer-binding W domain and the p21-binding A domain from the C terminus of Scar are both required to activate Arp2/3 complex. A proline-rich domain in the middle of Scar enhances the activity of the W and A domains. Preincubating Scar and Arp2/3 complex with actin filaments overcomes the initial lag in polymerization, suggesting that efficient nucleation by the Arp2/3 complex requires assembly on the side of a preexisting filament-a dendritic nucleation mechanism. The Arp2/3 complex with full-length Scar, Scar containing P, Wand A domains, or Scar containing W and A domains overcomes inhibition of nucleation by the actin monomer-binding protein profilin, giving active nucleation over a low background of spontaneous nucleation. These results show that Scar and, likely, related proteins, such as the Cdc42 targets WASp and N-WASp, are endogenous activators of actin polymerization by the Arp2/3 complex.