Epsins are the family of membrane proteins that are important in creating the needed membrane curvature. Epsins contribute to various needed membrane deformations like endocytosis and block vesicle formation during mitosis. Epsins have many different domains to interact with various proteins related to endocytosis. At its N-terminus is an ENTH domain that binds Phosphatidylinositol (4,5)-bisphosphate, meaning that it binds a lipid of biological membranes. It has also been postulated that this is a site for cargo-binding. In the middle of the epsin sequence are two UIMs (ubiquitin-interacting motifs). The C-terminus contains multiple binding sites, for example for clathrin and AP2 adaptors. As such, Epsins are able to bind to a membrane with a specific cargo and connect it with the endocytosis machinery, so one may understand Epsin as something like a Swiss army knife for endocytosis. They may be the major membrane curvature driving proteins in many clathrin-coated vesicle budding events. Epsin 4, which encodes the protein Enthoprotin, now known as Clathrin Interactor 1 (CLINT1), has been shown to be involved in the genetic susceptibility to schizophrenia in four independent studies. A genetic abnormality in CLINT1 is assumed to change the way internalisation of neurotransmitter receptors occurs in the brains of people with schizophrenia.
Epsin homologue of C.elegans is epn-1. EPN-1 conserves UIM, ENTH domain, and Clathrin-binding motif.