Ras dimerization is critical for Raf activation. Here we show that the Ras binding domain of Raf (Raf-RBD) induces robust Ras dimerization at low surface densities on supported lipid bilayers and, to a lesser extent, in solution as observed by size exclusion chromatography and confirmed by SAXS. Community network analysis based on molecular dynamics simulations shows robust allosteric connections linking the two Raf-RBD D113 residues located in the Galectin scaffold protein binding site of each Raf-RBD molecule and 85 Å apart on opposite ends of the dimer complex. Our results suggest that Raf-RBD binding and Ras dimerization are concerted events that lead to a high-affinity signaling complex at the membrane that we propose is an essential unit in the macromolecular assembly of higher order Ras/Raf/Galectin complexes important for signaling through the Ras/Raf/MEK/ERK pathway.

Ras 二聚化对于 Raf 激活至关重要。在这里，我们表明，Raf (Raf-RBD) 的 Ras 结合域在支持的脂质双层上的低表面密度下诱导强烈的 Ras 二聚化，并且在较小程度上在溶液中诱导强烈的 Ras 二聚化，如通过尺寸排阻色谱法观察到并通过 SAXS 证实。基于分子动力学模拟的群落网络分析显示，两个 Raf-RBD D113 残基之间存在强大的变构连接，该残基位于每个 Raf-RBD 分子的半乳糖凝集素支架蛋白结合位点，并且在二聚体复合物的两端相距 85 Å。我们的结果表明，Raf-RBD 结合和 Ras 二聚化是协同事件，导致膜上形成高亲和力信号复合物，我们认为该复合物是高阶 Ras/Raf/Galectin 复合物大分子组装中的重要单元，对于通过Ras/Raf/MEK/ERK 途径。