To form networks, the initial GFAP dimers combine to make staggered tetramers, which are the basic subunits of an intermediate filament. Since rod domains alone in vitro do not form filaments, the non-helical head and tail domains are necessary for filament formation. The head and tail regions have greater variability of sequence and structure. In spite of this increased variability, the head of GFAP contains two conserved arginines and an aromatic residue that have been shown to be required for proper assembly.
