Panchal Sanjay C, Kaiser Donald A, Torres Eduardo, Pollard Thomas D, Rosen Michael K
Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, Texas 75390, USA.
Nat Struct Biol. 2003 Aug;10(8):591-8. doi: 10.1038/nsb952.
Members of the Wiskott-Aldrich syndrome protein (WASP) family link Rho GTPase signaling pathways to the cytoskeleton through a multiprotein assembly called Arp2/3 complex. The C-terminal VCA regions (verprolin-homology, central hydrophobic, and acidic regions) of WASP and its relatives stimulate Arp2/3 complex to nucleate actin filament branches. Here we show by differential line broadening in NMR spectra that the C (central) and A (acidic) segments of VCA domains from WASP, N-WASP and Scar bind Arp2/3 complex. The C regions of these proteins have a conserved sequence motif consisting of hydrophobic residues and an arginine residue. Point mutations in this conserved sequence motif suggest that it forms an amphipathic helix that is required in biochemical assays for activation of Arp2/3 complex. Key residues in this motif are buried through contacts with the GTPase binding domain in the autoinhibited structure of WASP and N-WASP, indicating that sequestration of these residues is an important aspect of autoinhibition.
威斯科特-奥尔德里奇综合征蛋白（WASP）家族的成员通过一种名为Arp2/3复合物的多蛋白组装体，将Rho GTPase信号通路与细胞骨架联系起来。WASP及其相关蛋白的C端VCA区域（维普洛林同源区、中央疏水区域和酸性区域）刺激Arp2/3复合物形成肌动蛋白丝分支的核心。在这里，我们通过核磁共振谱中的差异线宽展表明，来自WASP、N-WASP和Scar的VCA结构域的C（中央）和A（酸性）片段与Arp2/3复合物结合。这些蛋白的C区域有一个由疏水残基和一个精氨酸残基组成的保守序列基序。这个保守序列基序中的点突变表明，它形成了一个两亲性螺旋，在生化分析中是激活Arp2/3复合物所必需的。这个基序中的关键残基在WASP和N-WASP的自抑制结构中通过与GTPase结合结构域的接触而被掩埋，这表明这些残基的隔离是自抑制的一个重要方面。
