This version of the C2 domain was initally identified in the vertebrate estrogen early-induced gene 1 (EEIG1) [1], and its Drosophila ortholog required for uptake of dsRNA via the endocytotic machinery to induce RNAi silencing [2]. It is also in C.elegans ortholog Sym-3 (SYnthetic lethal with Mec-3) and the mammalian protein EHBP1 (EH domain Binding Protein-1) that regulates endocytotic recycling and two plant proteins, RPG that regulates Rhizobium-directed polar growth and PMI1 (Plastid Movement Impaired 1) that is essential for intracellular movement of chloroplasts in response to blue light [2].

1: Identification of estrogen-responsive genes by complementary deoxyribonucleic acid microarray and characterization of a novel early estrogen-induced gene: EEIG1. Wang DY, Fulthorpe R, Liss SN, Edwards EA; Mol Endocrinol. 2004;18:402-411. PMID:14605097

2: Identification of novel families and classification of the C2 domain superfamily elucidate the origin and evolution of membrane targeting activities in eukaryotes. Zhang D, Aravind L; Gene. 2010;469:18-30. PMID:20713135