Molecular Biology Interdepartmental Program, University of California, Los Angeles, Los Angeles, CA 90095-1570, USA.
Mol Biol Cell. 2012 Oct;23(19):3801-13. doi: 10.1091/mbc.E12-04-0288. Epub 2012 Aug 8.
Formins are a conserved family of proteins known to enhance actin polymerization. Most formins are regulated by an intramolecular interaction. The Drosophila formin, Cappuccino (Capu), was believed to be an exception. Capu does not contain conserved autoinhibitory domains and can be regulated by a second protein, Spire. We report here that Capu is, in fact, autoinhibited. The N-terminal half of Capu (Capu-NT) potently inhibits nucleation and binding to the barbed end of elongating filaments by the C-terminal half of Capu (Capu-CT). Hydrodynamic analysis indicates that Capu-NT is a dimer, similar to the N-termini of other formins. These data, combined with those from circular dichroism, suggest, however, that it is structurally distinct from previously described formin inhibitory domains. Finally, we find that Capu-NT binds to a site within Capu-CT that overlaps with the Spire-binding site, the Capu-tail. We propose models for the interaction between Spire and Capu in light of the fact that Capu can be regulated by autoinhibition.
formin 是一类保守的蛋白质家族，已知其能增强肌动蛋白聚合。大多数formin 受分子内相互作用调控。果蝇 formin Cappuccino（Capu）被认为是一个例外。Capu 不含有保守的自动抑制结构域，可被第二种蛋白 Spire 调控。我们在此报告 Capu 实际上是受自动抑制调控的。Capu 的 N 端（Capu-NT）可强烈抑制成核和与延伸纤维的加帽端结合，这一过程由 Capu 的 C 端（Capu-CT）调控。流体力学分析表明 Capu-NT 是一个二聚体，与其他 formin 的 N 端相似。然而，这些数据与圆二色性分析相结合表明，Capu-NT 在结构上与先前描述的 formin 抑制结构域不同。最后，我们发现 Capu-NT 与 Capu-CT 内的一个位点结合，该位点与 Spire 结合位点，即 Capu-尾重叠。鉴于 Capu 可通过自动抑制来调控，我们提出了 Spire 和 Capu 相互作用的模型。
