This is the N-terminal domain of TTC7, a protein that forms the regulatory subunit of the PI4KIIIalpha complex (also known as PI4KA). This complex is composed of PI4KIIIalpha, TTC7 and FAM126A and catalyses the first step in plasma membrane phosphoinositide synthesis. This TTC7 N-terminal domain contains basic residues suitable for interaction with the acidic inner leaflet of the plasma membrane and is required for localising the active site near its substrate. TTC7 acts as a bridge between PI4KA and EFR3B-FAM126A, via direct interactions. ERF3B is not part of the complex but contributes to its recruitment to the membrane [, ].
Protein EFR3 homologue A (EFR3A) is a component of a phosphatidylinositol 4-kinase (PI4K) complex, composed of PI4KA, EFR3 (EFR3A or EFR3B), TTC7 (TTC7A or TTC7B) and FAM126 (FAM126A or FAM126B) []. This complex is required for the attachment of phosphatidylinositol 4-kinase (PI4K) to the plasma membrane. EFR3A is palmitoylated at its N terminus, anchoring the protein to the plasma membrane, and probably acts as the membrane-anchoring component in the complex []. In yeast, the Efr3p protein is a main regulator of the Stt4p phosphatidylinositol 4-kinase at contact sites between the endoplasmic reticulum and the plasma membrane [].
