Binds glycerophospholipids in a barrel-like domain and may play a role in cellular lipid transport (By similarity). Tethers the endoplasmic reticulum to the cell membrane and promotes the formation of appositions between the endoplasmic reticulum and the cell membrane. . This is the function of Ensembl gene identifier ENSG00000158220 (ESYT3, extended synaptotagmin 3).