Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, 565-0871, Japan.
Center for Biosystems Dynamics Research (BDR), RIKEN, Suita, Osaka, 565-0874, Japan.
Nat Commun. 2018 Nov 6;9(1):4635. doi: 10.1038/s41467-018-07035-x.
G protein interacting protein 1 (Gip1) binds and sequesters heterotrimeric G proteins in the cytosolic pool, thus regulating G protein-coupled receptor (GPCR) signalling for eukaryotic chemotaxis. Here, we report the underlying structural basis of Gip1 function. The crystal structure reveals that the region of Gip1 that binds to the G protein has a cylinder-like fold with a central hydrophobic cavity composed of six α-helices. Mutagenesis and biochemical analyses indicate that the hydrophobic cavity and the hydrogen bond network at the entrance of the cavity are essential for complex formation with the geranylgeranyl modification on the Gγ subunit. Mutations of the cavity impair G protein sequestration and translocation to the membrane from the cytosol upon receptor stimulation, leading to defects in chemotaxis at higher chemoattractant concentrations. These results demonstrate that the Gip1-dependent regulation of G protein shuttling ensures wide-range gradient sensing in eukaryotic chemotaxis.
G 蛋白相互作用蛋白 1（Gip1）在细胞质池中结合并隔离异三聚体 G 蛋白，从而调节真核趋化作用的 G 蛋白偶联受体（GPCR）信号。在这里，我们报告了 Gip1 功能的潜在结构基础。晶体结构显示，与 G 蛋白结合的 Gip1 区域具有圆柱状折叠，中央疏水性腔由六个α-螺旋组成。突变和生化分析表明，疏水腔和腔入口处的氢键网络对于与 Gγ 亚基上的香叶基化修饰形成复合物至关重要。腔的突变会损害 G 蛋白的隔离和从细胞质向膜的易位，从而导致在更高浓度的趋化剂下趋化作用缺陷。这些结果表明，Gip1 依赖性的 G 蛋白穿梭调节确保了真核趋化作用中的宽范围梯度感应。
