Enables identical protein binding activity. Involved in positive regulation of protein-containing complex assembly. Acts upstream of or within several processes, including extrinsic apoptotic signaling pathway; hematopoietic or lymphoid organ development; and regulation of hemopoiesis. Located in external side of plasma membrane and extracellular region. Part of CD95 death-inducing signaling complex. Is expressed in several structures, including alimentary system; brain; genitourinary system; hemolymphoid system gland; and liver and biliary system. Used to study Sjogren's syndrome; autoimmune lymphoproliferative syndrome; systemic lupus erythematosus; and type 1 diabetes mellitus. Human ortholog(s) of this gene implicated in several diseases, including autoimmune disease (multiple); cystic fibrosis; hematologic cancer (multiple); pre-eclampsia (multiple); and urinary system cancer (multiple). Orthologous to human FAS (Fas cell surface death receptor). [provided by Alliance of Genome Resources, Apr 2022]