EFR3 protein form a complex with Ypp1/TTC7 which is required to localise phosphatidylinositol 4-kinase (PI4K) to the plasma membrane. EFR3 acts as a regulator of the Stt4p phosphatidylinositol 4-kinase at contact sites between the endoplasmic reticulum and the plasma membrane [1-3]. EFR3 consists of armadillo repeats at its N-terminal, which act as a scaffold and a basic patch binds acidic phospholipids that anchors the complex to the plasma membrane [1].

1: Structural insights into assembly and regulation of the plasma membrane phosphatidylinositol 4-kinase complex. Wu X, Chi RJ, Baskin JM, Lucast L, Burd CG, De Camilli P, Reinisch KM; Dev Cell. 2014;28:19-29. PMID:24360784

2: EFR3s are palmitoylated plasma membrane proteins that control responsiveness to G-protein-coupled receptors. Bojjireddy N, Guzman-Hernandez ML, Reinhard NR, Jovic M, Balla T; J Cell Sci. 2015;128:118-128. PMID:25380825

3: Plasticity of PI4KIIIalpha interactions at the plasma membrane. Chung J, Nakatsu F, Baskin JM, De Camilli P; EMBO Rep. 2015;16:312-320. PMID:25608530