Defining feature of intermediate filament (IF)

310-355 residue coiled-coil domain in each IF molecule which is flanked by N- and C-terminal blobs. The base unit of the IF is a dimer where the 2 N-termini and C-termini are in close proximity and the coiled-coil region is wrapped around the other. These dimers associate laterally with each other in an anti-parallel fashion and make end-on-end contacts with other dimers where the N- and C-termini of adjacent dimers interact. This results in the formation of proto-filaments. Tetramers of proto-filaments are twisted around each other to form the mature IF. Note that formation of the IF is due to the intrinsic properties of the IF proteins and do not require any nucleators or adaptors.