The DP1 family of integral membrane proteins stabilize high membrane curvature in the endoplasmic reticulum and phagophores. Mutations in the human DP1 gene REEP1 are associated with Hereditary Spastic Paraplegia type 31 and distal hereditary motor neuropathy. Four missense mutations map to a putative dimerization interface but the impact of these mutations on DP1 structure and tubule formation are unknown. Combining biophysical measurements, functional assays, and computational modeling in the context of the model protein Yop1, we found that missense mutations have variable effects on DP1 dimer structure and in vitro tubulation activity, and provide mechanistic insights into the role of DP1 oligomerisation on membrane curvature stabilization. Whereas the mutations P71L and S75F decreased dimer homogeneity and led to polydisperse oligomerization and impaired membrane curving activity, A72E introduced new polar interactions between subunits that stabilized the Yop1 dimer and allowed robust tubule formation but prevented formation of more highly-curved lipoprotein particles (LPP). The introduction of a BRIL domain to the cytoplasmic loop of A72E rescued LPP formation, consistent with a requirement for dimer splaying in highly curved membranes. These results suggest that the membrane curving activity of DP1 proteins requires both dimer stability and conformational plasticity at the intermolecular interface.

中文翻译：

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Yop1 稳定性和膜曲率产生倾向受其寡聚化界面控制。


整合膜蛋白的 DP1 家族稳定了内质网和吞噬细胞中的高膜曲率。人 DP1 基因 REEP1 突变与 31 型遗传性痉挛性截瘫和远端遗传性运动神经病有关。4 个错义突变映射到一个推定的二聚化界面，但这些突变对 DP1 结构和肾小管形成的影响尚不清楚。在模型蛋白 Yop1 的背景下结合生物物理测量、功能测定和计算建模，我们发现错义突变对 DP1 二聚体结构和体外管活性有不同的影响，并为 DP1 寡聚化对膜曲率稳定的作用提供了机制见解。突变 P71L 和 S75F 降低了二聚体的同质性，导致多分散寡聚化和膜弯曲活性受损，而 A72E 在亚基之间引入了新的极性相互作用，稳定了 Yop1 二聚体并允许形成稳健的小管，但阻止了更高弯曲脂蛋白颗粒 （LPP） 的形成。将 BRIL 结构域引入 A72E 的细胞质环中挽救了 LPP 的形成，这与高度弯曲膜中二聚体张开的要求一致。这些结果表明，DP1 蛋白的膜弯曲活性需要分子间界面的二聚体稳定性和构象可塑性。