Structural domains comprising this superfamily share the structure of the N-terminal subdomain of the C-terminal domain of the exocyst complex subunit Sec15. The exocyst is important for exocytosis in yeast and is required for targeting and docking vesicles to specific membrane sites during budding. The exocyst is evolutionarily conserved from yeast to human. The yeast exocyst is found in sites where active exocytosis and membrane addition take place, and functions as an effector of Sec4p, a vesicle-associated Rab GTPase. Sec15p links Sec4p and downstream fusion effectors at discrete cellular locations. Its C-terminal domain mediates Rab GTPases binding which occurs in a GTP-dependent manner PMID:16155582.